(CNN) - Mitt Romney on Thursday pushed back against Senate Majority Leader Harry Reid's allegations that the presumptive GOP nominee has not been paying his taxes.
"It's time for Harry to put up or shut up," Romney said on Sean Hannity's radio show.
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In a Huffington Post interview published Tuesday, the leading Democrat said that an unnamed investor with Bain Capital, Romney's former private equity firm, told Reid in a phone conversation that Romney had not paid taxes for a decade.
Reid stood by the allegations on Thursday while speaking on the Senate floor.
"The word's out that he hasn't paid any taxes for 10 years," he said. "Let him prove he has paid taxes because he hasn't."
Democrats and President Barack Obama's re-election campaign have repeatedly called for Romney to release more tax documents to answer any questions about his financial portfolio.
Romney has made public the full 2010 tax return and an estimate for 2011, with a pledge to release the full year once it's complete. He filed an extension for an October deadline.
Critics have hit back against Reid's comments this week, faulting him for making claims based off an anonymous source.
"Harry's gonna have to describe who it is he spoke with because of course that's totally and completely wrong," Romney said Thursday in the radio interview. "It's untrue, dishonest and inaccurate. It's wrong. So I'm looking forward to have Harry reveal his sources and we'll probably find out that it's the White House."
Mirroring Romney's comments, senior campaign adviser Eric Fehrnstrom described Reid's comments as "shameful, pathetic, baseless and untrue" and argued the majority leader, with the help of the Obama campaign, was attempting to "engage in McCarthy-like accusations about Mitt Romney."
"Four years ago Barack Obama said he was going to come to Washington and change the politics. Instead the Obama campaign has turned into a bottomless pit. Every day they reach a new low," he said Thursday on CNN's "The Situation Room."
Adding on, Fehrnstrom said Romney has "never zeroed out his tax liability" and "has always paid 100% of what was owed."
After Romney's interview on Hannity's radio show, the majority leader responded in a statement and said he is not backing down from his remarks.
"As I said before, I was told by an extremely credible source that Romney has not paid taxes for ten years. People who make as much money as Romney have many tricks at their disposal to avoid paying taxes," he said.
Reid argued Romney is "hiding something" and called on the presumptive GOP nominee to release more taxes.
"When it comes to answering the legitimate questions the American people have about whether he avoided paying his fair share in taxes or why he opened a Swiss bank account, Romney has shut up. But as a presidential candidate, it’s his obligation to put up and release several years’ worth of tax returns just like nominees of both parties have done for decades," Reid said.
According to a source familiar with Reid's thinking, the majority leader, a former boxer, considers himself a political street fighter now, willing to throw a punch and get hit back big time for a cause. In this case, the cause is making sure the topic of Romney's tax returns remains in the news, and in the campaign narrative.
The source said Reid is "happy to mix it up and put this back in the news" and added the "finger waggers of the Acela corridor won't dissuade him from speaking his mind."
Reid, the source said, is unconcerned about the hits he is taking on making unsubstantiated claims, because the Democratic base is fired up. The source says they know that anecdotally. It's not an accident that Reid said this to the Huffington Post, a friendly outlet, and did so as Romney was returning from his overseas trip.
"What happened when Romney returned? The first story he has to deal with is his tax returns," the source said.
One of Romney's biggest surrogates, Sen. John McCain of Arizona, came to Romney's defense on Thursday, saying Reid may have "gone over the line."
"I've known Sen. Reid for many, many years, and occasionally he displays some rather erratic behavior," McCain said on CNN's "Anderson Cooper 360." "To accuse someone of doing something without a shred of proof–that the allegation has any substance–is really something I, frankly, don't understand."
McCain, whose 2008 presidential campaign reviewed Romney's tax records as they considered him to be the vice presidential running mate, said last month he can "personally vouch" that there was "nothing disqualifying" in the tax returns of the presumptive GOP presidential nominee.
On Thursday, he urged Reid to come "forward" with his source.
"I think politics are tough. I enjoy the give and take but I think Harry might have gone over the line," McCain said.
Later, while visiting a fruit stand with his mother in Florida, Ryan responded to the negative reaction in the room.
"Entitlement reform has unfortunately been made very partisan by partisans, and so I have gotten that kind of reaction and unfortunately it's what we come to expect because the politics of reforming entitlements has become very bitter and it's very unfortunate," he told reporters in Lakeland.
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.... And the IRS is just giving Romney a pass on a decade of taxes?? Reid is an idiot.
so Romeny accuses Reid of an anonymous source wihotut any proof, then he has the nerve to claim it is Obama again without any proof? what a dope! does he not understand he just lowered himself to reid's level?
No, it's time for Romney to put up or shut up. If he has in fact paid taxes and not dodged them with every loophole in the tax code, he needs to prove it. It's painfully obvious he's hiding something.
Just show the darn tax returns to prove you didn't avoid paying all of your taxes. Mitt had no problem using his father's money to start up Bain, so he needs to use his father's transparency.
Hey Mitt, an easy way to shut Reid up....show the returns and prove him a liar. Or do you have someting to hide?
Romney can resolve any and all tax questions by simply producing his tax returns. Why isn't he doing so? By not producing them, it looks like he has something to hide.
We bet Mittens 10,000 dollars he is the liar andhe can put up or shut up by showing 10 years of his tax returns and if he did pay ten years is the proof. Now, Put Up or Shut Up. Sincerely, 10,000 Americans
Obama released his birth certificate. If Romney wants to say he did not zero out his liability and paid all he owed, then he should prove it. Release the taxes, or it looks like he is hiding some really bad stuff. Man up and release the taxes or take what you get.
Romney can dispell all the rumors by realeasing 12 years worth of tax returns just like his dad did when he ran for president..Or perhaps what Sen Reid says IS true!! Reid can match Mitt tax return for tax return and let US decide who is hiding some..But We all know Mittt is not going to release his tax returns because we would see jsut where he is putting all that money in off shore accounts and in Swiis bank accounts,then so much for being for the "average" worker...
Mittens I think you protest too much. You put up or shut up. How convenient that you took an extension until Oct for your tax return. If you have nothing to hide then show the Country your 2009 tax return.
Why should he have to show more than 2 years of returns?
I want to see the taxes. What's he hiding? Just show us the taxes. Reid's probably right...he didn't pay any.
If Romney really wants to discredit Reid, all Romney has to do is release his tax returns. Easy solution, unless he has something to hide.
OK hold on Mr Reid you sound like you are assuming facts not in evidence. So ease off the making these charges .
Now ity would be nice to see more of any candidates tax returns, party not with standing.
Romney is the one who needs to put up or shut up in regards to his taxes. Just show them and the questions will all go away... or is he too dense to understand that?
Romney.....the burden of proof lies with you....You put up or shut sir.......
i would urge mr. romney to come forward with those 10 years of tax returns. put up or shut up indeed!
although i dont agree with the tatic i understand what reid did. Every other presidential candidate releases more than 2 years of tax returns just in a effort to show how squeaky clean they are but romney wont do that so reid is trying to make him angry enough to do it. You have to be completely transparent with almost every aspect fo your work/ business and financial life if you want people to trust you to run the country
release your taxes like everyone else
Romney needs to put up. Until he does I'll have to assume he paid no taxes and vote accordingly.
Mitt should save this bluffing for the poker table. SHOW YOUR TAXES MITT.
yes..."put up" those tax returns and Harry will "shut up"...unless you're hiding something.
I would say that Romney needs to "Put out" or "shut up!" He won't release his tax returns because he is hiding something!
Say what you want about the man but Reid is a political genius.
So let me get this straight – Romney blasts Reid for making unproven claims about him, then in the next breath he says the accusation must have come from the WH? Without a shred of evidence?