In a new ad by an independent group:

I'm doubtful that these types of attacks will work. So is Nate Silver:

Obama may not have persuaded that many voters on Friday night (I don't think his performance, frankly, was all that persuasive). But he may have reassured and locked in some of his soft supporters -- perhaps Clinton voters and working class Dems. What that means is that Obama's floor is higher (and therefore McCain's ceiling is lower). What it also means is that negative attacks may be less effective for McCain, which are often targeted at soft supporters of the opposing candidate.

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