The new Fox News/Opinion Dynamics poll, which gives Obama a 7-point edge, has some numbers on whether the issue of Bill Ayers is affecting voters.

* 61% said Obama's association with Ayers made no difference on whether they would vote for him; 32% said it would make them less likely to vote for him.

Breaking the numbers down:

* 64% of Independents said no difference; compared with 29% who said less likely.

So it appears as if Ayers is making some difference, but not a lot, as Independents don't seem particularly concerned about it.

UPDATE: Marc Ambinder makes a good point:

To truly drive Ayers into the public conversation, to trick what they consider an irredeemably biased press corps into biting, McCain has three vehicles gassed up and ready to go.

(1) He could put lots of money into an Ayers ad -- video press releases don't cut it.
(2) He could devote a stump speech to Obama's associations and Obama's associations only
(3) He could mention Ayers in a debate.

So far, McCain has done none of those things.

Indeed, McCain has taken a strange path with the Ayers stuff. He and Palin mention him on the stump; the campaign has made Web ads; but apparently the campaign isn't ready to go all in.