I agree with both Madsen Pirie and Nigel Evans. It's going to be May 2010 before there's an election. Here's my reasoning: Gordon Brown is a cautious man. He's not just one who plans long and carefully; that would be admirable. Instead he's one who goes into a tizzy when things don't go exactly to plan. His bottling out of an autumn election at the last minute was characteristic. It wasn't George Osborne on the death tax, it was a poll of the key marginals which frightened him.
As PM he gets to choose, barring accidents. He'll want a time when he has a sustainable lead in the polls, a long-term one that cannot be overturned in the heat of an election campaign. There isn't going to be such a lead. The economy has turned against him, and people are feeling poorer because of too many price increases. The reputation for economic competence foundered on the Northern Rock, and any remaining reputation for probity disappeared into the pockets of anonymous and third party Labour donors.
No lasting poll lead translates into no election until he hits the wire in spring 2010 and has to call one. Then he loses and David Cameron becomes prime minister. Simple, really. Pity it's all going to take so long.