I don't know if 30% is some kind of Mendoza line or not, but I do know that Bush in 2004 never went below 47% - even at the height of the Abu Grahib.
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I went back to look at which candidates' money line was most similar to McCain. And in early October, 2000 then Gov. Bush was down to about 30%.
So as dark as things look right now, I still don't think we are "playing for next year," if, as shown above, things start moving McCain's way very soon.