Harper is hoping to call an election because Dion has proven himself to be a completely inneffectual leader. Even supporters of the Liberal party don't believe in him. Dion has absolutely zero charisma and won't be able to convinece Canadians of anything.
He's been threatening an election all year, but all that's for show. He has to show his supporters he's doing SOMETHING even though he knows he can't.
Canadians laugh at him, his party is broke, and nobody wants ANYTHING to do with his retarded carbon tax plan. I don't think the Liberals could have made things any easier for the Conservatives in a fall election.