Jacob Heilbrunn sees tonight’s debate as the moment Romney’s campaign could end “in all but name”:

It is Romney’s last shot. If he can emancipate himself from GOP dogma, he’ll have a fighting chance. He won’t simply be battling Obama but also his own party, which views him with deep mistrust. But if he fails, he may take it down along with him and set the stage for Obama to win big.

This may exaggerate the number of obstacles that Romney has to overcome. The debate will be difficult enough for Romney without having to “battle” his own party. If Romney spends much time trying to “emancipate” himself from prevailing Republican views, that will just prompt a new round of articles about Romney’s troubled relationship with his own supporters, and it will cause another week of movement conservative teeth-gnashing. Anything that draws attention at this point to Romney’s reputation as an unprincipled and untrustworthy candidate is worse for him than any specific policy position he might take.

Tonight’s debate is not Romney’s “last shot,” but it is almost certainly his best available shot. Domestic policy issues are naturally far more important to almost all voters, so there is at least the potential to win over some doubters. Barring some major event in the next few weeks, people voting on foreign policy have already made up their minds one way or the other, but Romney might still be able to win over some remaining undecided voters on the issues being discussed tonight. That poses its own challenges, since Romney usually trails Obama on most of these issues, too, but at least he leads on one or two of them. Romney is theoretically more prepared and much stronger on these issues than he is on foreign policy. (I know, that’s not saying much.) These are supposed to be at the heart of the campaign’s case against Obama. After tonight, Romney’s opportunities will become fewer and the chance of a major mistake increases as the debates shift more to foreign policy. Unless Romney is widely perceived to have had the better performance, everything becomes much more difficult for his campaign. His campaign won’t be finished if he is judged the loser (assuming he doesn’t fail completely), but he will have lost the best opportunity remaining to him.