Obama camp: What is Romney hiding by withholding tax returns?

— -- One day after President Barack Obama pressed Mitt Romney to be an "open book" on his personal finances, the incumbent's reelection campaign released a new web video suggesting that the Republican standard-bearer may be hiding something improper by refusing to release more of his tax returns.

The online attack features CNN's Wolf Blitzer asking former Republican National Committee Chairman Haley Barbour whether Romney should release his information, and Barbour replying: "I would." (Not featured: Barbour telling Blitzer that the issue didn't amount to " diddly" in the campaign).

The video showcases media suggestions that Romney might have eluded American taxes by parking money in places like the Cayman Islands and mocks Romney's response as "Just take our word for it." "The American people deserve the facts," the ad says.

It shows Romney sidestepping the issues in Republican primary debates, saying "maybe" and "time will tell" when asked whether he will follow his father George Romney's standard-setting decision to release a decade's worth of tax returns.

"How long can Romney keep information on his investments in overseas tax havens secret? And why did he do it in the first place? Time will tell," the ad says.

Romney took steps to counter the attack on Tuesday, insisting he has little to do with the management of his personal investments because they are in a blind trust. "I don't manage them," Romney said in an interview with Radio Iowa's O. Kay Henderson. "I don't even know where they are."

Responding to reports that some of his investments have been overseas, Romney insisted his "trustee follows all U.S. laws." He added: "All the taxes are paid, as appropriate. All of them have been reported to the government. There's nothing hidden there." And he charged that Obama "is going to try to do anything he can to divert attention from the fact that his jobs record is weak."

Regardless of the merits of the criticisms, they seem to serve a similar political purpose to the "Swift Boat" attacks of the 2004 campaign: Undermine a vital part of the challenger's resumé. Democratic Senator John Kerry relied heavily on his past as a decorated Vietnam War veteran to argue he was better suited to be commander-in-chief amid profound public anger about the war in Iraq. The tax return assault targets Romney's argument that his background as a hugely successful investor makes him better suited to be chief executive amid profound public anger about the economy.

Democrats, unsurprisingly, hate the comparison, arguing that the false Swift Boat attacks were beyond even the lax standards of political campaigns. Some Republicans in Washington worry that Romney could make the same mistake that Kerry did: Letting the attacks go unanswered (or poorly answered) to such a degree that they hamstring his core argument on the number one issue in the election.