How Many Voters Are Still Persuadable?

Why Douthat will be keeping an eye on the polls:

I think the next week’s worth of polling will tell us a lot about how fluid this race might be down the stretch, and how many undecideds and persuadables still remain. Barring some unexpected turn in world events, it’s hard to imagine Romney having a better moment (and enjoying better media coverage) than he will after a performance like last night’s trouncing of the president. Over the next week or so, then, I would expect him to earn a polling bounce at the high end of the historical average from debates: Per my colleague Nate Silver, that would be about three points, which would leave the race more or less dead even. But if he only gains a point or so in the poll of polls, on the other hand, then that’s a clear sign that the two coalitions are really pretty much locked in at this point, and that even though the race is tight Romney’s path to victory remains extremely difficult to map. And if he gains more than three points … well, then a lot of conservatives will start tuning in to MSNBC just for the schadenfreude.