President Obama’s campaign is out with a new ad going hard after Mitt Romney to release his past tax returns.

The former Massachusetts governor has released his 2010 tax return and released an estimate of his 2011 taxes, with a pledge to release the full return. But he has resisted giving more information about his past taxes. Obama’s ad seizes on that fact, saying it “makes you wonder if some years he paid any taxes at all. ”

“Tax Havens. Offshore accounts. Carried Interest. Mitt Romney has used every trick in the book,” the narrator says. “Romney admits that over the last two years he’s paid less than 15 percent in taxes on $43 million in income. Makes you wonder if some years he paid any taxes at all. We don’t know because Romney has released just one full year of his tax returns. And won’t release anything before 2010.”

A clip plays of Romney telling an interviewer, “You know what, I’ve put out as much as we’re gonna put out.”

The ad concludes, “What is Mitt Romney hiding?”

The ad mixes the facts we know about Romney’s taxes — which remind viewers of his wealth — with pure speculation.

“With no rationale for reelection and no plan to help middle-class Americans, President Obama has resorted to running a campaign of distraction, distortion and dishonesty,” said Romney spokeswoman Amanda Henneberg.

But, just as with his Bain Capital record, Romney’s unwillingness to release more information makes it hard for him to respond.

Romney told Radio Iowa last week that a trustee manages his investments and “all the taxes are paid, as appropriate. ... There’s nothing hidden there.”

“Makes You Wonder” is airing in Pennsylvania, where Romney will campaign today.