I'm sure a party like the Greens could be convinced to lend support if one of their policies was promised for a push. It'd be a bit makeshift getting all those minor parties to lend support and likely they'd not be able to convince enough of them anyway but its what I'd go for. When a lot of your voters are opposed totally to the Tories and are voting Libdem as they perceive the Libdems "to be to the left of labour" it just seems suicidal to throw your lot in with the Tories.
The Greens have one seat in parliament. 1. Did you even look at the make up of parliament when I asked you the question?
Plaid Cymru: 3
So even with those three in board you still only have 325. A five party coalition that just sneaks into majority land (as Sinn fein don't take seats). 5 defections from your 5 party coalition on any vote and you lose. 5 parties to have 10 more votes than the opposition.
Bear in mind the crucial fact-THe Liberal Demcrats could not afford to fight another election. They could not afford to not co-operate beccause they had for years called for more coalition governments and had to show they were a worthwhile vote.
And as for that coalition, the SNP wanted an exemption of Scotland from cuts. Labour were still at that point lead by the man who called a voter a bigot behind her back and was universally hated across the country. They were so useless in 2010 that when they first tried to talk to the Liberal Democrats their representatives did not even have an agreed position. (plus one of their negotiators was Lord Mandelson, and another was Ed Balls, two of the foulest men in politics today)
Then just to make sure all those voters vanish permanently Clegg had to open his big mouth and say there is no future to them being to the left of labour (it was totally unneeded statement). The only thing I can't figure out is where all those votes are going to funnel into; oddly many might actually go to UKIP, some back to labour and perhaps some might go to Respect who actually is left wing (but have a bad rep due to the media painting a high Muslim membership as some sort of crime).
UKIP I doubt it as a main plank of Lid Dem support is pro-EU. They will either not vote or go to Labour.
Respect are not unfairly painted anything. Their fat useless !@#$head of a leader said it was ok to rape women a while ago. !@#$@#$ scumbag.