Quite predictably, John McCain has been running ads to recruit Hillary Clinton fans over to his side. I don't know how effective this will be for him, but it merits a response, especially with the pick of Palin as VP, which seems like a real (cynical) attempt to get disaffected women over to McCain's side.
Here's the kind of advertising response that might work for Obama (or better yet, for state parties or 527s), especially in fairly conservative districts. The point here is mainly to produce a backlash for McCain's use of Hillary's words; perhaps something that may make his camp think again."
[note: this is off the top of my head; some of the claims I make about Clinton's record may not be true exactly, but you all can think of better ones anyway]
"So John McCain has been encouraging Hillary Clinton supporters to join him in his race for the White House. [image: the most milquetoast photo of McCain that anyone can find, on one part of screen; McCain "hillary" ad running in other corner of screen]
"But let's remember what Hillary Clinton stands for." [image: faded Clinton photo, looking strident, becomes sharper, joining McCain. Then, behind these photos, a series of newspaper headlines and still photos drift across the screen; imagine them filled with scary images and headlines that reinforce the messages in the following text]
"Hillary Clinton is pro-choice; she supports civil unions, and even marriage for same-sex couples; she has voted again and again against the Second Amendment; as First Lady to the most liberal president of the last 40 years, she attempted a government takeover of our health care system" [foreground image: as the First Lady line is read, Bill's face emerges from the background images and joins McCain's and Hillary's onscreen, emerging from behind but dominating the screen].
"and Hillary Clinton supports secular judges for the nation's highest courts.
"If John McCain thinks Hillary Clinton's supporters would be right at home in his campaign, just what does John McCain believe, anyway?"
[I am snarky snarkerson, and i approve this message]