Obama said during Monday night's debate that the sequester "will not happen." Republicans say they were taken aback by the comment, and there's been speculation that this could weaken his bargaining power during the fiscal cliff negotiations.
If anything, Obama was simply asserting with greater confidence that Congress will, in fact, manage to come up with some kind of fiscal bargain that undoes the sequester. At the same time, he's insisted over the past year that not just any deal will do, using the veto threat to insist that the bargain must include revenues and deficit reduction, not just repealing the sequester cuts.
And that's Obama's biggest threat — and the Republicans' biggest fear: not the automatically triggered sequester cuts, which no one wants, but the expiration of the Bush tax cuts for the wealthy, which the president insists must be included in any fiscal cliff deal under threat of a veto.
That said, how Congress actually gets there is unclear: All we're hearing right now are the alarm bells about the apocalyptic impact of the sequester and the rest of the fiscal cliff, while neither party is pushing publicly for a deal yet. That could explain why so many were surprised when Obama asserted that a resolution would happen.