Here's what I don't understand about McCain's (almost certainly spontaneous) announcement that Obama has forced him to bring up Ayers tonight: If McCain goes that route, doesn't that mean he's mostly wasted the last several days, when he and Palin have substantially toned down their Ayers rhetoric? (Days he can hardly afford to waste, I might add.) It seems strange to pursue one strategy in the days leading up to a debate, then another strategy during the debate--particularly when the strategies are contradictory. And even if they weren't contradictory, wouldn't you want to lay the groundwork for an attack before leveling it?
On the other hand, as Chris says, if McCain doesn't mention Ayers tonight, he's going to get hammered in the press for making empty threats (cue the erratic meme) and essentially wimping out.
So, all in all, well played!