(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.
– Ryan gives House GOP a 'pep talk'
– Defending Romney, McCain cites 2008 campaign trail misspeak
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– Pawlenty takes post at Financial Services Roundtable
– Letterman: No hard feelings toward Romney
All Romney has to do is show his tax returns like every other presidential candidate and this will end. This shows us what kind of president Romney would make – sneaky and arrogant.
more distraction and subversion from the left to take America's attention off the poor economic growth and climbing unemployment numbers under Obama. They really are masters of deception.
Mitt, there's an easy way to prove Reid wrong.
Like I said before, Romney and Spiro Agnew are cut from the same cloth.
Stop hiding your tax returns, unless you've got something to hide.
"You people don't need to know who my sources are. You're not getting anything more out of me."
– Harry Reid 2016
Romney to Reid: 'Put up or shut up'
said the guy that won't show his tax returns
If Reid is wrong, Romney can prove it: just produce those tax returns, Mitt.
Hey Rmoney, show me yours and I will show you mine.
Humm. Well, Mr. Romney can quell this argument by releasing his tax returns. That would prove whether Mr. Reid is right or wrong.
I find this all very troublesome. Considering the GOP does the exact same thing, accuse someone of something, with out proof or facts.. What is good for the goose is good for the gander, according to my Grandmother.
If Romney paid "100% of what he owed", why not just show us? As it would be a simple way to stop this particular argument and because he is not forthcoming, it's obvious those tax returns will put him in a bad light. Romney needs to "put up or shut up"; it's time.
Show us the tax returns Mitt!
I find this all very troublesome. Considering the GOP does the exact same thing, accuse someone of something, with out proof or facts.. What is good for the goose is good for the gander, according to my Grandmother. So Mitt is accusing the whit house as Reid's source. No proof or facts. So how are they different
This makes no sense, The only person to "put up or shut up" is Romney, by releasing his tax returns through his time at Bain. Harry Reid is just asking what all Americans are asking, what does Romney have to hide? If he has nothing to hide just release his returns. Next Romney will be saying the old Nixon refrain, "I am not a crook." Just what we need in the White House, another Nixon and scandal.
It seems that Romney should "put up", isn't he the one applying for the job? Show the voters your tax returns, Mitt!
How about you just release your tax returns and prove him wrong then, Mitt?
McCain is on record vouching for Romney's tax returns. We shall see if McCain is a liar.
Romney is hiding something and its pretty obvious. He has refused to come clean-what else don't we know about him? Must be something so serious he is running scared. We need Wikileaks and Anonymous to dig up the truth.
You want to embarrass Harry Reid? Call his bluff and release your tax returns. PROVE HIM WRONG THAT YOU'VE NOTHING TO HIDE. Otherwise, save the self-righteous indignation for someone who cares.
Romney is the one who should put up or shut up. It's a legitimate question (how much has a Presidential nominee paid in taxes over the past 10 years?) and his reluctance to be transparent speaks volume about his forthrightness. Most of us can't hide behind blind trusts, hidden bank accounts, and crafty tax lawyers when it comes to paying taxes!
Apparently, Reid thinks that this is a valid tactic. What a winner.
And all Romney has to do is produce is tax returns. He's hiding something. Probably something illegal. Goodness knows he hasn't produced his birth certificate, so he could be an illegal alien not paying taxes on income made in the U.S.
Harry Reid should release his taxes too.
Harry Reid will end up eating crow if or when Romney does release more Tax information.
Or he will be charge with a Federal crime for illegal access to or use of private tax information. (May not get charged while Obama is in office since Obama is the Lead in the Obstruction of 'Equal Justice Under the Rule of Law'.)
Romney needs to put up or shut up – let's see the full tax returns going back to his days at Bain.