According to this Politico article, Romney understands that he isn’t likely to win tonight’s debate:

Mitt Romney has a clear-eyed and self-aware view of his chances in the final debate Monday, according to top advisers: It will be almost impossible to win, since the debate is focused exclusively on foreign policy, a strength for President Barack Obama.

Since Romney is generally expected to lose tonight, the more interesting political aspect of the debate is whether that loss will be a large or a very small one. Narrowly losing a foreign policy debate might be enough to limit damage to the Republican ticket’s standing. Barring a major error by Obama, the debate’s impact on the election will depend on whether Romney performs well enough to be perceived as competent or appears once again to be out of his depth.

Based on his public statements, Romney’s understanding of these issues ranges from poor to mediocre, and the more he is forced to answer in detail the more difficult things will become for him. Obama’s goal will be to draw him into exchanges that force him to do this, and the extent of Romney’s loss will be determined by how often Romney can escape from those exchanges without blundering. Romney’s goals will be to survive the evening without inflicting any major wounds on himself, and to distinguish himself from George W. Bush enough that most viewers don’t think his foreign policy would be a disaster waiting to happen.

The expectation that Obama will win the debate tonight creates the potential for an upset, but that would require that Obama make a major mistake that is widely recognized as such. If Obama says something that hawkish ideologues think is a major mistake, it probably won’t have been a mistake at all. On the other hand, if Obama retreats into the old “defensive crouch” on national security and has to keep invoking counter-terrorism to change the subject he won’t receive much credit for winning the debate. Considering how heavily favored Obama will be going into this debate, a narrow win isn’t what his campaign needs.

The greatest danger for Romney is that he sabotages himself by repeating attack lines that only hawkish ideologues find credible. That would show that he is either just mouthing their phrases or so intent on proving that he is a hawk that he doesn’t care how politically harmful their hard-line policies are. For example, if he returns to dated, nonsensical complaints about the Green movement protests or missile defense, he wouldn’t land any hits on Obama’s record and he would demonstrate how much he relies on the movement conservative echo chamber for his arguments. The less that he sounds like the candidate who delivered the VFW and VMI speeches, the better it will be for him politically. A reliable standard for judging how well or badly Romney has performed is to see how the most ideological neoconservatives respond to what he says in the debate. If they are extremely pleased by his performance because he echoed their views, Romney will have lost the debate very badly indeed.