Readers, with the Liberal Democrats in such decline after their many betrayals, suck-ups to the Conservative Party, and failure to uphold their values, it is no wonder that in many local by-elections, local elections, and parliamentary by-elections, they have been bettered in polls by such a wide variety of different candidates. The Green Party is now regularly bettering the Liberal Democrats in many polls, on that note.
Here is a list of minor party (the major parties other than the Lib Dems are the Conservatives, the Greens, Labour, and UKIP; the SNP and Plaid Cymru are also major parties in Scottish- and Welsh-related contexts respectively) and independent candidates who have beaten the Lib Dems over the span of the Con-Dem government's time (which is due to expire soon next year):
2011, Barnsley Central: BNP and Independent Tony Devoy.
2012, Bradford West: Respect MP George Galloway.
2012, Rotherham: BNP, Respect, English Democrats and Independent Simon Copley.
2013, South Shields: Independents Ahmed Khan and Phil Brown, and the BNP. The OMRLP came tantalisingly close (only 155 votes behind the Lib Dems here)
2014, Newark: Independent Paul Baggaley (who only needed 50 votes more to keep his £500 deposit)
In Scottish local elections and by-elections:
2013: No Bedroom Tax, TUSC, Borders Party, various independent candidates.
2012: (depending on area): Christian Party, Scottish Socialist Party, TUSC, Glasgow First, Borders Party, and most notably, a man dressed in a penguin suit.
In Welsh local elections and by-elections:
2014: Llandaff North Independents, TUSC, a few other independents.
2013: Socialist Labour (in Ynys Mon Assembly by-election), TUSC, one independent.
2012: (depending on area): TUSC, independent.
In English local elections and by-elections (parties with at least two candidates having beaten the Liberal Democrats in two separate wards):
2014: TUSC, Socialist Labour, Make Willesden Green, National Health Action, Harrow's Independent Labour Group, People Before Profit, All People's Party, Peace Party, Respect, Pirate Party, the (continuing) Liberals, English Democrats, British Democrats, BNP, National Front, (and infamously once in Clifton North, Nottingham), the Bus Pass Elvis Party.
Also, one thing I have noticed is the astounding drop in the Liberal Democrat share (in comparison to their 2010 vote share in the respective seat, by terms of how much of the vote share they lost) in by-elections compared to increases/decreases in Labour and Conservative vote shares during the last four years:
By-election: Lab vote share +/-: Con vote share +/-: LD vote share +/-:
& Saddleworth +32.9 -51.5 +0.9
Barnsley Central +28.5 -52.0 -75.8
Leicester South +26.8 -29.4 -16.3
Inverclyde -3.9 -17.5 -83.5
Feltham & Heston +24.8 -18.5 -57.0
Bradford West -44.8 -73.0 -61.7
Manchester Central +31.1 -61.9 -64.7
& Penarth +21.6 -29.7 -51.6
Corby +25.4 -37.0 -65.8
Rotherham +4.0 -67.7 -86.9
Middlesborough +31.8 -66.5 -50.2
Croydon North +15.5 -30.3 -75.0
Eastleigh +2.1 -35.4 -31.0
South Shields -3.1 -46.8 -90.0
& Sale East +25.4 -43.1 -78.0
Newark -21.0 -16.5 -87.0
Clacton -55.2 -53.6 -89.4
& Middleton +2.0 -54.8 -77.5
& Strood -41.0 -30.1 -94.7
Meanwhile, we Greens have always increased our vote share (and in some cases the number of votes we got in 2010 in the respective seat) in Parliamentary by-elections so far in the coalition government's tenure, excepting only Bradford West. And this was even before our recent surge this year.