Sure, Dion is stumbling, the Bloc is weak, the NDP increasingly irrelevant. But ideally, what Harper wants (needs) is Canadians to get comfortable with a Conservative government. The Conservative's inability to approach the magical 40% mark in the polls, means that they are not quite there yet. Going to the polls after only a year in office does not lend credibility to the Conservative claim to be able to govern the nation.
For this reason it would behoove Harper to stay in office for another year, and if he can stay relatively scandal and gaffe free, chances are more middle of the road Canadians will gravitate towards his Conservative Party. This is especially true if Harper can herd the cats that are the opposition parties, this would build on his already growing reputation as a true leader.
Current poll results put the Liberals with anywhere from 28-34% support. This represents the inherent value in the Liberal brand, not support for Dion.
If an election were called, the contest suddenly becomes Harper vs. Dion. When that direct comparison is made, support for Harper jumps to over 50%. This does seem like a great reason to have an election.
Is there a danger that Dion might suddenly become a competant leader in the course of a year? Maybe. But the likelihood is that he will continue to falter, and the longer he is out there, the louder the whispers from the back of the room will get. How long before Ignatieff's and Rae's people openly brandish their knives, rather than quietly plotting in Ottawa steakhouses as they do now? Best to leave the lid on that stew, and let the pressure build.
So while there are some advantages in going to the polls now, patience is a virtue, and could lead to a majority.