Barack ObamaBarack Hussein ObamaObama opens up about singing 'Amazing Grace' after Charleston shooting: 'I've used up all my words' Exclusive: How Obama went to bat for Warren Why the 'Never-Trumpers' flopped MORE's latest ad criticizes John McCainJohn Sidney McCainCindy McCain planning 'intimate memoir' of life with John McCain Trump-McConnell rift divides GOP donors Arkansas state senator says he's leaving Republican Party MORE for picking Alaska Gov. Sarah Palin (R) as a running mate.

The spot knocks McCain's knowledge about economics and then questions his pick of Palin. The ad then cuts to a video of Palin at the vice presidential debate winking at the camera.

Marc Ambinder writes that a heartbeat-like sound plays in the background, perhaps to convey that Palin could be a heartbeat away from the presidency. The Obama campaign called that interpretation "absurd."

The campaign said the spot will start airing "across the country" on Thursday.