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Obama is the favorite, but it's incredibly silly to pretend he's some kind of shoo-in. No political professional or expert thinks that, and neither do Vegas oddsmakers. Nor is it supported by environmental factors like the economy, even if it improves. Nor is it reflected in his approval rating. There's really nothing to support the idea that this is a foregone conclusion.
This is especially true when the primary reason for favoring him heavily is the perceived strength of his eventual opponent. That's a horrendously flawed, subjective measure. For example, Ronald Reagan was thought the riskier choice when he ran in the primaries against Bush Sr. in 1980, a perception which was stupendously wrong.
So sure, I'd bet on Obama. I'd put him at a little over 60% if I had to. But it'd be crazy to give him more than, say, 2-1 odds at the absolute most.