Even if you don't accept the argument that John McCain made things worse with the bailout negotiations yesterday, I don't see how he possibly could claim things are any different.
So based on the standards he set on Wednesday, there's no reason he should be heading to the debate tonight.
It's tempting to say that he blinked, but it's not like he was squaring off against someone and finally gave in. If anything, he was squaring off against himself.
The important point is that for any thinking person, every single moment he stands on that stage tonight will expose his utterly irrational (erratic?) behavior.
And it comes during the debate focused on national security. I just can't imagine a worse scenario for McCain going into the debate.
Though I guess the upside is that it lowers expectations...