Obama to Romney: Release more tax returns President Obama and his top aides took aim at Mitt Romney Thursday night, calling on the likely Republican presidential nominee to release more of his tax returns and questioning whether he has used loopholes to avoid publicly disclosing more information about his personal wealth. Seizing on a Washington Post report that Romney is using an exception in federal ethics laws to avoid disclosing the full extent of his investment holdings, Obama sent three tweets under his personal Twitter name attacking Romney. In his final tweet, the president wrote: "So what's Romney hiding? Tweet @MittRomney to demand he release his tax returns. #WhatsRomneyHiding. Obama's first tweet drew attention to The Post's story: "The Washington Post reported today that Mitt Romney is using a loophole to avoid disclosing his financial records: http://OFA.BO/svM9ND." The president's second tweet quoted his campaign manager, Jim Messina: ."@Messina2012: "Each week, new questions are raised about whether [Romney] took unusual steps to avoid paying his fair share in taxes."" In a statement, Messina accused Romney of having "put his personal financial assets in a black box and hid the key." Messina called on Romney to release more than the two years of tax returns he released in February. "Governor Romney provided 23 years worth of tax returns to the McCain campaign so they could determine if he would make a suitable vice president," Messina said, referencing Sen. John McCain's vetting of Romney in 2008. He must meet that same standard now so that the American people may judge whether he would be a suitable president, and whether there are any conflicts of interest that could cloud his judgment. Romney campaign spokeswoman Andrea Saul responded to Obama's tweets by saying that the former Massachusetts governor's assets have been disclosed as required by the law in his personal financial disclosure. Saul suggested that if the Office of Government Ethics had considered any part of Romney's filing "insufficient, it would have made it clear." "President Obama will do anything to try and distract Americans from his failed record of chronic unemployment, lower incomes and higher gas prices," Saul wrote in a statement. Shortly after Obama sent his tweets, Romney senior adviser Eric Fehrnstrom tweeted: "Yikes, it just cost me $4.09/gallon to fill up in Boston! #Obamaisntworking." The engagement signaled that the general election is already underway, even though three other Republican candidates remain in the race and Romney has not yet clinched the nomination. At a campaign fundraiser in Washington Thursday night, Obama went after Romney by name, repeating an attack the president made in a speech Monday going after his would-be opponent for his support for Rep. Paul Ryan's controversial budget proposal. "We are going to have a big and important debate in this country, and I cannot wait," Obama told donors. We have tried what they are selling. We tried what they are peddling and it did not work. We have spent the last three years cleaning up after some of that mess and I don't want to do it again. Obama added: "This is going to be a big debate and it's going to be a fun debate. It's always good to have the truth on your side. But it's not going to be easy. We're going to have to work hard. A lot of folks out there are still struggling.