Six months ago, I wrote a run-down on how likely the 60 most marginal Conservative seats and also the 25 most marginal Liberal Democrat seats would be lost or held by the respective incumbent parties.
However, in the last six months, there has notably been a decline in the support of both Conservative and Labour (although this varies from constituency to constituency in practice) and pleasingly the Green Party has been able to maintain a steady support base of 7-8% (in one or two polls, we have even polled 10%!). Meanwhile, the Liberal Democrats' support and UKIP's support has been flat-lining, as both parties have been consistently polling 6-7% and 14-15% respectively over the last few months. Also, since Scotland voted 'No' in the independence referendum which took place a month after I made that last prediction of marginal seats, I will now factor Scottish constituencies into this new prediction.
With more and more candidates coming forward, not just for the five largest parties but also for many others (as well as considerable numbers of Independent candidates), anything could happen in many of these marginal seats.
Predictions for Britain's 80 most marginal major party seats (NB: order is in vote majority by number of votes, not percentage):
1. Hampstead & Kilburn: Of the three-way marginal seats in Britain, this is the tightest-and Glenda Jackson is standing down-and there is also a relatively strong Green potential. Even though much of the Liberal Democrat vote that switches will likely go to Labour, a Labour hold in this seat is by no means certain due to the tightness of the contest that will occur in this seat. Likely Labour hold-but watch out for a surprise.
2. North Warwickshire: As I have said before, the fact that Dan Byles is standing down when he only had a majority of 54 votes, UKIP's potential in this seat, and the weak Liberal Democrat base, will all contribute to Mike O'Brien surely regaining the seat he lost in 2010. Dead cert Labour gain.
3. Camborne & Redruth: It is now clear to me that a Lib Dem re-gain is rather unlikely, but is still more likely than a Labour gain even though this is the only seat in Cornwall where Labour will make even a reasonably strong showing. With UKIP having strong potential to split the Conservative vote (and potentially even win this seat themselves), and with a large number of candidates, this is a difficult seat to call. Too tight to call.
4. Thurrock: This has been often been talked about as the second most likely UKIP gain in the UK this year, behind only South Thanet. Labour will be trying hard to regain it, though. Dead cert Conservative loss-either to Labour or UKIP.
5. Bolton West: In my honest opinion, the Conservatives have missed their best chance to gain this seat, particularly when the altered boundaries were more favourable to Labour. UKIP's showing in Bolton West was also above average in 2010, but I must note that their rise will hurt both the Labour and Conservative vote share. Likely Labour hold.
6. Oldham East & Saddleworth: Another case of 'missed opportunity they probably will not get again for a long time', this time for the Liberal Democrats, who in my opinion would have gained the seat in 2010 had ex-MP Phil Woolas not unlawfully smeared his Liberal Democrat opponent, Elwyn Watkins (who is not standing here in 2015), who is the only Lib Dem candidate to have increased the Lib Dems' vote share in any by-election this parliament (although only by 0.3% on 2010). The Lib Dems' severe decline, especially in urban seats like this one, will ensure a Labour hold by Debbie Abrahams in my opinion. Dead cert Labour hold.
7. Hendon: Apart from increased Green potential, nothing much has changed in the last six months regarding political potential in Hendon. I still believe Andrew Dismore will get his seat back. Dead cert Labour gain.
8. Sheffield Central: The Lib Dems were so close to winning this seat in 2010, because of the high student vote-this time around, it is the Green Party who will mainly benefit from the student/academic vote that exists here. However, there is also a high core Labour vote which will mean a hold is likely for now. Likely Labour hold.
9. Solihull: With a strong Green advance, and at least some Labour recovery likely here, this seat will almost certainly fall to the Conservatives even though their vote share will be hit as well, and Solihull will probably still remain marginal. Dead cert Conservative gain.
10. Oxford West & Abingdon: The Lib Dems have been holding up better than they have in Solihull, but both Labour and the Greens will inevitably nip at their heels, and there is not much potential for UKIP either. Nonetheless, this will remain a tight contest. Likely Conservative hold.
11. Ashfield: This is rather interesting due to the substantial advance Lib Dem candidate Jason Zadrozny made in 2010 (he is re-standing). However, Gloria De Piero will probably have an incumbency bonus that will likely stave off not only UKIP's attempts to win over ex-Labour voters (an important factor in many ex-mining seats like this one) but also the Lib Dems' best efforts. Likely Labour hold.
12. Southampton Itchen: One of a bare handful of possible Conservative gains from Labour in this year's election-John Denham is standing down and the candidate who nearly gained it in 2010, Royston Smith, is standing again. UKIP's rise could play a decisive role in whether this seat changes hands or not. 50/50 Labour hold/Conservative gain.
13. Cardiff North: The fact that Labour is now struggling to stay ahead or to peg level with the Conservatives in polls will not make any difference now in this seat, due to the fact Jonathan Evans is retiring and the fact Labour can win over many ex-Lib Dem voters. Dead cert Labour gain.
14. Sherwood: Even if Labour's support declines slightly rather than increases, (which has been seen in some Ashcroft polls in various English seats) a Conservative majority of 214 is not enough to prevent UKIP's rise undermining them fatally in Sherwood. Dead cert Labour gain.
15. Mid Dorset & North Poole: Now that there is a Green candidate in this seat (and the Green Party will take a significant number of Lib Dem votes in the South West) and even with vote-splitting between the Conservatives and UKIP, the Lib Dems have no realistic chance of holding this seat (in my last prediction, I believed they did due to the weak Labour base and UKIP's high potential). Dead cert Conservative gain.
16. Norwich South: The Green Party is in a better position to win Norwich South than six months ago, although Labour will still try hard to win this seat back. Dead cert Liberal Democrat loss-either to Labour or the Green Party.
17. Edinburgh South: Out of all the Labour seats in Scotland, this one has the worst SNP potential by a considerable margin-and potentially, Lib Dem voters here may be more inclined to vote Labour this year to counteract any (nevertheless large) surge in SNP votes that could occur here. Probable Labour hold.
18. Stockton South: Not much change six months on-realistically, the fact remains that the Conservative majority in this seat is too low to stop Labour regaining it in May. Dead cert Labour gain.
19. Lancaster & Fleetwood: This has good long-term potential for the Green Party (one Ashcroft poll for this seat showed them in a reasonably good third place), but this year, the main point is that Labour will have no real trouble winning this seat, even if the Conservative to Labour swing remains low (e.g. 1-2%), due to its knife-edge majority. Dead cert Labour gain.
20. Bradford East: Not only is there a small majority, but David Ward has not done himself any favours in his tenure as this seat's MP. Even if David fares better than some other Lib Dem MPs who had won their seats from Labour, he will almost certainly lose due to the fact the Lib Dems will be hit hardest in urban seats. Dead cert Labour gain.
21. Broxtowe: Anna Soubry is quite a bit different from many Conservative MPs in a few positive ways, but Nick Palmer is almost assured to win his seat back for Labour since in Con-Lab marginal ex-Lib Dem voters are generally more likely to shift from Lib Dem to Labour than from Lib Dem to Conservative. Dead cert Labour gain.
22. Truro & Falmouth: Unlike Camborne & Redruth, the Liberal Democrats may still have some chance here to re-gain, in spite of Truro & Falmouth being better for Labour than Truro & St Austell (which existed from 1997 to 2010), because of UKIP's reasonably high potential to win over ex-Conservative voters. However, the student population resident in Falmouth could also be somewhat promising to the Greens (if not to the extent of St Ives). 50/50 Conservative hold/Liberal Democrat gain.
23. Swansea West: The Lib Dems came very close to winning in 2010, but in 2015, their vote share will fall backwards quite heavily, especially since it is a Lab-LD marginal and not a Con-LD/LD-Con marginal. There is potential for the Green Party to advance here compared to many other Welsh seats, but not enough to give Geraint Davies any trouble in holding this seat. Dead cert Labour hold.
24. Newton Abbot: Another of the bare handful of possible gains for the Lib Dems this year-UKIP did very well last time as well, which will come into consideration. However, strong Green potential in Devon and the fact the Labour vote will recover will probably scupper Richard Younger-Ross' chances of regaining his seat, even if not by much. Probable Conservative hold.
25. Wirral South: Despite the marginality I do not believe the Conservatives have any real chances of winning this one-and Esther McVey's tenure as MP in neighbouring Wirral West will probably have a negative effect on the Conservative vote here in the same way that David Owen's tenure as an MP in Plymouth Devonport helped spark an increase in the SDP/Liberal vote shares of Plymouth Drake and Plymouth Sutton in 1987. Likely Labour hold.
26. Chesterfield: As ex-MP Paul Holmes (not to be confused with a serial Liberal Party candidate in Cornwall of the same name, by the way) is not standing again, the Lib Dem vote will slip back heavily, and much of it will as with 2010 slip back to the Conservatives as well as to Labour, making this a safe Labour seat once again after May 2015. Dead cert Labour hold.
27. Amber Valley: The recent 'Candy Crush' controversy of Amber Valley's MP, Nigel Mills, will not mean much difference in my opinion-a Labour gain is almost certain in any event. Dead cert Labour gain.
28. Derby North: Like Northampton North, I believe that last time around, the Liberal Democrats simply worked hard and got lucky in a traditional marginal where they did not initially have much of a base. I believe much of it will likely return to Labour and enough ex-Conservative votes will also return to Labour to make sure Chris Williamson is in no real danger of losing his seat. Dead cert Labour hold.
29. Kingston-Upon-Hull North: The Lib Dems did very well to nearly take an otherwise safe Labour seat in 2010, with a swing of 12% in their favour-they will fall back even further this time. UKIP will probably take some Labour votes as there is not much of a Conservative vote left to hit, but that overall will likely only make a superficial difference. Dead cert Labour hold.
30. Dudley North: A UKIP gain is possible here-and so is an accidental Conservative gain from Labour depending on what happens in the campaign in this constituency. One to watch this May. Probable Labour hold-watch out for surprises, though.
31. Wolverhampton South West: As I said in my last seat by seat prediction of the most marginal seats, this was once safely Conservative but not anymore. A re-gain for Rob Marris (MP for this seat from 1997 to 2010) will likely not be a problem for Labour. Dead cert Labour gain.
32. Great Grimsby: One of Labour's most likely losses at the next election outside of Scotland. However, much of the Lib Dem vote successively built up by Andrew de Freitas (who is not re-standing for the Lib Dems) could fall in Labour's favour to hold off UKIP's strong advance. 50/50 Labour hold/UKIP gain.
33. Waveney: The Greens will do well here, which could affect the Labour vote in addition to the comparatively weak Lib Dem vote, but UKIP will probably hurt the Conservative vote more. With only a triple-figure Conservative majority, it is very likely Bob Blizzard will win his seat back. Dead cert Labour gain.
34. Wells: UKIP has been having local problems here, which could dampen their chances of splitting the Conservative vote, which is Tessa Munt's only realistic chance of holding her seat in a place where the Lib Dem vote will suffer a substantial decline. Likely Conservative gain.
35. Carlisle: As I said six months earlier, the relative prosperity of this seat amongst seats in the north west of England will not be enough for the Conservatives to hold here when it is so marginal. Dead cert Labour gain.
36. Morecambe & Lunesdale: In this once safely Conservative seat (until it was gained by Labour in 1997), UKIP's rise will dash any real hopes of the Conservatives holding on. Not much more to say even though the swing to Labour will be pretty low. Dead cert Labour gain.
37. Rochdale: Simon Danczuk's 'old Gaitskellite' style populism might not go down well in some quarters (some have said that he could potentially defect to UKIP in the future, but the heavy collapse in the once strong Lib Dem vote in this seat that will occur in May will mean that he will have no trouble in holding Rochdale. Dead cert Labour hold.
38. Telford: The Conservatives narrowly missed this time around, and the UKIP rise that will occur in many traditional Lab-Con marginal seats will likely put the Conservatives out of play in Telford for the foreseeable future. Dead cert Labour hold.
39. Walsall North: There was a good effort by the Conservatives to win Walsall North from Labour last time, but the substantial potential for UKIP will muddy the electoral waters here. However, this could just possibly cause Labour to lose as well-another seat worth keeping an eye on. Probable Labour hold.
40. Weaver Vale: Not much to say here-a Labour gain is very likely when the swing needed is only just over 1%, and there are as usual Liberal Democrat votes for Labour (and the Greens, to a lesser extent) to win over. Dead cert Labour gain.
41. Harrogate & Knaresborough: Similar prediction to six months ago-Conservative hold likely with the Lib Dem vote unwinding. Likely Conservative hold.
42. Lincoln: This seat may lose its bellweather status-because there is a small chance that nationally, the Conservatives could (just) remain the largest party despite making a net loss in seat terms, but this seat is likely to fall to Labour in May. Likely Labour gain.
43. Morley & Outwood: The Conservatives nearly caused Labour to suffer their own 'Portillo moment' in 2010-but in 2015 they and the Lib Dems will fall back enough so that Ed Balls will not worry too much about holding his seat. Likely Labour hold.
44. Plymouth Sutton & Devonport: This seat will feature one of the heaviest collapses in Lib Dem vote shares this year-which will benefit both Labour and the Greens. UKIP is also strong here, though, making this an interesting one to watch-that said, Labour is likely to win here. Likely Labour hold-but watch this seat.
45. Montgomeryshire: This would be a Liberal Democrat seat now had it not been for the antics of Lembit Opik-Glyn Davies is only the second Conservative MP to represent Montgomeryshire since 1880. (Delwyn Williams defeated Emlyn Hooson in 1979 but was himself defeated in 1983 by Alex Carlile.) UKIP have their best prospects in Wales here (and Labour almost their worst; Montgomeryshire is the only Welsh constituency to have never had a Labour MP) which could bring down the Conservative vote enough for the Lib Dems to re-gain it, but this is not that likely. Probable Conservative hold.
46. Brighton Pavilion: Despite the fact the minority Green administration in Brighton and Hove is not that popular, the hard work Caroline Lucas has done for her constituents, for the green movement, and for leading a real opposition in the House of Commons means she is likely to retain this seat in spite of the efforts Labour will make to capture it. Likely Green hold.
47. Birmingham, Edgbaston: In spite of the relative prosperity of Edgbaston amongst Birmingham constituencies, I think Labour will not have much trouble holding this marginal seat despite a strong Conservative effort that will likely happen here as with 2010. Likely Labour hold.
48. Stroud: This seat has one of the strongest potentials for the Green Party in the UK both short-term and long-term. That said, David Drew is likely to regain Stroud which he had held from 1997 to 2010; UKIP is not that strong here but can still undercut the Conservatives. Dead cert Labour gain.
49. St Austell & Newquay: Tricky to call-the Lib Dems are holding up well in many parts of Cornwall, but Dick Cole, leader of Mebyon Kernow, has a strong personal vote and he could very well play a decisive role in the outcome of this seat. However, this could still be a good bet for the Lib Dems. Probable Liberal Democrat hold.
50. Brighton Kemptown: A key marginal which the Conservatives are likely to lose to Labour-although the Green Party is well-placed to take votes from both Labour and the Liberal Democrats. Likely Labour gain.
51. Brent Central: With Sarah Teather standing down (the only reason the Liberal Democrats ever gained its predecessor seat, Brent East, in the first place), and with the Lib Dem vote about to collapse in many urban seats where they had made some headway, a Labour win is pretty much a foregone conclusion. Dead cert Labour gain.
52. Bedford: Patrick Hall appears almost certain to re-gain Bedford for Labour due to UKIP splitting the Conservative vote, even if the Lib Dem vote in Bedford is more resilient than most. Dead cert Labour gain.
53. Watford: This seat will be contested vigorously-especially with current Watford Mayor Dorothy Thornhill as Lib Dem PPC-Watford may indeed be the only Lib Dem gain in the country this year, if any are made at all. Richard Harrington is rather anonymous amongst Conservative MPs but there is a chance he may still hold due to a split ticket-Labour may be in third place but they are doing better locally in Watford than the Conservatives. Too tight to call.
54: Arfon: Arfon is not as safe for Plaid Cymru as its predecessor Caernarfon was, but unlike most Labour MPs, Hywel Williams has actually opposed the Con-Dems resolutely, alongside other MPs from Plaid Cymru, SNP's 6 MPs, and Green MP Caroline Lucas; this should see him through. Likely Plaid Cymru hold.
55. Halifax: Linda Riordan is standing down as Labour MP here but there is little to suggest her successor will not hold the seat-even if the Conservative vote does not take much of a hit, the Lib Dem vote will. Likely Labour hold.
56. Dewsbury: UKIP did not stand here last time but will this time-and since it is unlikely Khizar Iqbal (an independent candidate who split the Labour vote) will stand again, Dewsbury is practically certain to the Labour fold. Dead cert Labour gain.
57. Newcastle-under-Lyme: The Conservatives came somewhat close to winning this seat in 2010 (by 1,552 votes; this is notable since there has not been a Conservative MP in Newcastle-under-Lyme since 1906) despite UKIP achieving one of their best results then, especially by the standards of Labour-held seats. UKIP has substantial local strength in Newcastle-under-Lyme but that will just hold the Conservatives back in the long term. Dead cert Labour hold.
58. Warrington South: A bell-weather seat likely to fall to Labour, depending on where some ex-Lib Dem voters go-some may turn Conservative though. Finally ex-Labour councillor Kevin Bennett is a TUSC candidate there, and even if he only polls a few hundred votes those may count for something in a 3-way marginal. Likely Labour gain.
59. Plymouth Moor View: Whether Labour can hold this seat depends on which type of ex-major party votes UKIP in Plymouth wins over most; the Liberal Democrat vote collapse will probably benefit Labour enough, however. Likely Labour hold.
60. Sutton & Cheam: The Liberal Democrats have proved surprisingly resilient in Sutton-UKIP efforts have undermined Conservative efforts to regain lost ground, and will actually help the Lib Dems retain Sutton & Cheam (and similar seats elsewhere like Hazel Grove and Eastleigh where in spite of the Lib Dem strength the Green Party does not have good potential). Likely Liberal Democrat hold.
61. Wakefield: Not much to say here-a Labour hold is almost assured since UKIP will stand this time around (there was no UKIP candidate in Wakefield in 2010). Dead cert Labour hold.
62. Newport East: The Liberal Democrats were quite lucky to get reasonably close in 2010 in an otherwise safe Labour seat-which will likely become safe again after May 2015. Dead cert Labour hold.
63. Pudsey: In spite of Pudsey having fared the recession better than many constituencies in the north of England, a Labour gain is pretty likely-but there is still some chance of a Conservative hold. Likely Labour gain.
64. Eltham: Another marginal the Conservatives missed last time-and the Conservatives have fallen back heavily in some parts of London. I cannot see a reason why Labour should lose Eltham this year. Dead cert Labour hold.
65. Enfield North: Notionally a Conservative hold in 2010, but the swing was pretty low and this seat is rather marginal. I think Labour can be confident of winning even if not by much (the core Conservative vote in Enfield North is considerable). Dead cert Labour gain.
66. Middlesbrough South & East Cleveland: Little to say-both partners in the Con-Dem coalition will fall back, and if Labour's vote share falls here (unlikely) it still will not really endanger their chances of a hold. Dead cert Labour hold.
67. St Ives: This is one of the best seats in terms of long-term potential for the Green Party-St Ives has been rather progressive in terms of demographics for years. However, Andrew George's somewhat rebellious nature as a Lib Dem MP gives him a fighting chance. Probable Liberal Democrat hold.
68. Edinburgh North & Leith: Like Edinburgh South, the fact that middle-class Lib Dem voters here are probably more Labour-inclined than SNP-inclined could save Labour here if tactical voting occurs. Probable Labour hold.
69. Walsall South: Like Walsall North, UKIP's efforts may prove decisive in whether Labour holds this seat or not-but for now, a Labour hold seems more likely than not. Probable Labour hold.
70. Nottingham South: A Labour hold is practically certain in Nottingham South despite this seat not being safe-UKIP has undercut the Conservatives locally quite severely and will do so at the general election. Dead cert Labour hold.
71. Somerton & Frome: David Heath is standing down and David Rendel is not likely to replace him, especially given his particular Liberal Democrat stance. The Conservative vote share will be hit significantly by UKIP, but in all likelihood not enough to prevent them taking this seat. Likely Conservative gain.
72. Burnley: Like Rochdale, there will be a substantial Lib Dem collapse here, even if not to the same extent as Rochdale, and enough of it will return to Labour, even with UKIP on their tail. Dead cert Labour gain.
73. Blackpool South: Fracking has become a prominent issue in Blackpool, which will help the Green Party in both Blackpool seats-but that is likely to hit the Liberal Democrat vote more than the Labour vote. This is another case of how UKIP's undercutting of the Conservative vote will dash any realistic chance of a Conservative gain. Dead cert Labour hold.
74. Gedling: As with many Nottinghamshire constituencies, UKIP's rise and the Lib Dems' decline will generally be beneficial to Labour-apart from this I have not much to say. Dead cert Labour hold.
75. Hove: Even if Mike Weatherley was standing again (which he is not) his notorious 'anti-squatting' legislation would probably cost him enough votes to lose him his seat in May 2015. Meanwhile, UKIP is nipping at the Conservatives' heels and the traditional liberal vote in Hove will largely swing in the Greens' favour. However, a relatively recent Ashcroft poll showed a low swing from Conservative to Labour here, so there is at least an outside chance of a (narrow) Conservative hold. Likely Labour gain.
76. Manchester Withington: Out of all the Liberal Democrat seats, the biggest collapse in the Lib Dem vote will happen here-possibly even to the point where the Green Party wins second place or at least third place (this seat's demographics are very Green-friendly as well as once Lib Dem-friendly) in the poll. As has often been repeated, the bell tolls for John Leech. Dead cert Labour gain.
77. Corby (gained by Labour in 2012 by-election): This is pretty much a fait accompli-Andy Sawford is pretty much assured of holding the by-election gain he made for Labour over two years ago. Dead cert Labour by-election hold/general election gain.
78. Brentford & Isleworth: Last year's local elections in London saw the heaviest Conservative defeat locally in Hounslow, and the fight for the substantial Lib Dem vote here will fall more in Labour's favour than the Conservatives. The potential for UKIP is not that good, particularly in middle-class Chiswick which lies in this constituency, and Green potential in Brentford & Isleworth will be reasonable but not enough to worry Labour too much. Likely Labour gain.
79. Northampton North: On paper, this ended up being more marginal than Watford in 2010-and this is a reliable bell-weather seat with relatively average demographics socio-economically. Whether this is held by the Conservatives or gained by Labour could depend on whether Labour maintains its narrow national lead or loses it. Probable Labour gain-but watch this seat.
80. Hastings & Rye: Lacking the relatively high prosperity of most South-East constituencies, and with a majority of just under 2000 for the Conservatives, a Labour gain is very likely indeed, even with the Green Party able to poll reasonably from a standing start, Respect having selected a PPC here and UKIP unlikely to do particularly well (Rye and the surrounding villages are still rather genteel compared to the town of Hastings in my opinion). Likely Labour gain.
There are of course many other constituencies likely to change hands in this election, as the UK enters an era five party politics (six party politics in the case of Scotland and Wales). This election will certainly be one to remember, for decades thereafter.