"His defeat is now imperative."

Yup. John Judis bottom-lines it:

That's a long way of saying that it is simply unpatriotic--it's an insult to flag, country, and all the things that McCain claims to hold dear--for McCain to hold this financial crisis hostage to his political ambitions. McCain doesn't know a thing about finance and is no position to help work out an agreement. If we do suffer a serious bank run, or a run on the dollar, it can be laid directly at his feet. As I said to friends last night, if McCain had been president at this point, I would have wanted to impeach him.