The recent by-election in Oldham East and Saddleworth is a curious affair for a number of reasons starting with the courts overruling the General Election result and stripping Phil Woolas of his seat for his controversial election pamphlets. Ordinarily the party of government fares badly in these votes where there loss of vote from the general election result is used as some sort of referendum on their performance. In this case, however, we have two partied in government with the last MP a Labour member expelled for wrong doing - not a common circumstance. The public could have easily punished Labour for the dirty tactics of Woolas as comment on the Coalition. As it happened the Tories took a back seat to allow Labour's closest rivals, the Lib Dems a chance at winning the seat but as the Tory vote collapsed the Lib Dem vote stayed the same as borrowed Tory votes replaced those disenfranchised liberals who went back to Labour.
http://www.bbc.co.uk/news/uk-politics-12191431

   In an interview the Tory MP Mark Pritchard (who has had a busy week after swearing at the Speaker http://www.bbc.co.uk/news/uk-politics-12195973 ) seemed happy with the Conservatives not campaigning too heavily on the proviso that their Coalition partners reciprocated whenever a by-election occurred that the Tories were better placed to beat Labour. In seats with a three way split all bets were off apparently. This is assuming that voters who put their cross next to Lib Dem last time would vote Conservative. No doubt there will be a loyal group who will be happy to support the Coalition but if there share of the vote only stayed the same with Tory support it indicates that they are more likely to switch to Labour. Presumably Mr Pritchard and his colleagues are aware of this and are merely glossing over the poor showing that the Conservatives had by claiming it as a favour for their new friends. By-elections in this parliament could be more interesting than usual.