Three new ads in the presidential race mix this week. Barack Obama goes Negative Lite with a new McCain = Bush montage featuring a reworked version of Sam Cooke’s “Wonderful World,” the McCain campaign scratches at the Obama/Clinton scab by giving the spotlight to a Hillary supporter who’s voting for McCain, and a third-party outfit called the American Issues Project coughs up a 1-minute spot tying Obama to former Weather Underground leader William Ayers.

In Obama’s “Don’t Know Much,” a vaguely James Taylor-ish crooner spins couplets like “I’m not up on the economy/ Don’t know much about industry/ Really can’t explain the price of gas/ Or what has happened to the middle class” while on-screen chiros quote McCain on his ignorance of economics and reprise The Hug.

Barack Obama: “Don’t Know Much” (:30)

McCain’s new ad is a testimonial from one Debra Bartoshevich, a former Hillary delegate who says she will vote for John McCain. It’s timed so as to keep the chattering classes playing up Obama/Clinton antagonisms during the Democratic convention. Also relevant: The latest USA Today/Gallup poll says that 27 percent of Clinton backers currently plan to vote for McCain.

John McCain: “Debra” (:30)

And in the first full-on Swiftboating episode of the campaign, a nonprofit group called American Issues Project is pushing an ad that highlights Barack Obama’s past association with a U of Illinois professor and former Weatherman, William Ayers, who served on a community board with Obama in Chicago. The ad, which Fox News channel declined to air for unspecified reasons, is appearing in heavy rotation in some swing states (Michigan, Ohio, Pennsylvania, and Virginia, according to TPM’s Greg Sargent), where $3 million is being spent on ad buys.

The American Issues Project is headed by a former consultant to McCain’s Iowa campaign, Ed Failor Jr., is also the executive VP of the anti-tax group Iowans for Tax Relief.

American Issues Project: “Know Enough?” (1:00)