Graham said Reid was “making things up,” and Republican National Committee Chairman Reince Priebus called Reid a “dirty liar” for leveling the accusations against Romney, the presumptive Republican presidential nominee.

“I just cannot believe that the majority leader of the United States would take the floor twice, make accusations that are absolutely unfounded in my view and, quite frankly, making things up to divert the campaign away from the real issues,” Graham, a South Carolina Republican, said Sunday on CNN’s “State of the Union.”

Reid, a Nevada Democrat, made the allegations in a Senate floor speech last week. His office repeated the charge in a statement issued today.

“As Senator Reid has said, an extremely credible source informed him that Mitt Romney did not pay taxes for ten years,” Adam Jentleson, Reid’s spokesman, said in an e-mailed statement. Jentleson said Romney was trying to “hide the truth” by not releasing his returns from previous years.

Romney has released one year of personal income tax returns, from 2010, showing that he paid an effective tax rate of 13.9 percent on investment income that year. He has promised to release his 2011 returns when accountants are finished with them, and has rejected calls by Democrats and some within his own party to disclose more of his tax returns.

Axelrod Call

Priebus on ABC’s “This Week” said he wouldn’t respond to a “dirty liar who hasn’t filed a single page of tax returns himself.”

David Axelrod, an Obama campaign strategist, said he didn’t “know who Harry was talking to.” At the same time, Axelrod, speaking on “Fox News Sunday,” repeated calls for Romney to release more returns.

“The Romney campaign and Governor Romney can resolve this in 10 seconds,” Axelrod said. “Why don’t they just put this to rest? What is it he’s hiding?”

Virginia Governor Bob McDonnell, a Republican, said on CBS’s “Face the Nation” that Reid had made a “reckless and slanderous charge.”

“People don’t care about Mitt Romney’s tax returns,” McDonnell said. “They care about their own tax returns.”

Former Pennsylvania Governor Ed Rendell, a Democrat, said on “Face the Nation” that voters want to know whether presidential candidates “pay their taxes fairly like everybody else.”

Rendell also said Romney’s tax returns are “not a central issue” in a campaign that has focused on the economy.