(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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Harry thinks he can say anything he wants to , and Mitt will have to disprove it . I say Harry needs to prove his lie , if he can .
On a lighter note , someone told me Harry was seen soliciting sailors down on the docks .
I think that Reid left out a word or two - fair portion. I think that Romney did pay some taxes, but he paid far less than he could have and should have. Income taxes shouldn't seperate capital gains and income that comes from a paycheck. That is what allows Romney to pay less if anything at all.
It's up to you Romney to put up, or shut up. Prove Reid wrong by showing us your tax returns.
This could all go away for Romney if....
All Romney has to do is release his tax records to prove Reid's allegations are untrue. If he has nothing to hide, why hide it?
If Romney has nothing to hide, why not release his tax records?
Romney is affraid of the truth...plain and simple. He is not releasing these tax forms because he wants to hide the truth. Can you blame him? If the truth be told the only votes he would get would be from the 1%'ers, that plus asking advice on how to pay ZERO taxes on 1/4 BILLION dollars.
If his tax returns are on the up n up, then why not release them. He should put up and end this distraction. We the people deserve more than just one year and probably one more this coming October. WE the PEOPLE deserve much better from someone who wants to hold the highest job in the land.
Romney-You "Put Up Or Shut Up!". It's time we see 10 years worth of you corrupt, "zeroed out" tax returns. This isn't goin' away slick...
Dear Mitt, no returns= no presidency, my my but life can be so simple sometimes.
Hey Mittens!!! PUT UP or SHUT UP!!!
show the papers Mitt. Pretend you are a voter.
I think that Mitt should show his tax returns ...all of them i think that Mitts secrets are coming back to haunt him
Telling someone to "put up or shut up" is a little different than telling him to "shut up." I hope Reid has evidence. If not, nail the man to the wall.
I thnk Mitt is the one who needs to ut up or shut uip. There's only one reason to refuse to release your tax returns. There's only one reason to have bank accounts in the Caymans, Bermuda, Switzerland. Only ONE reason. C'mon people, we've known this forever.
Sen. Reid should release his 2005-2010 tax returns to show Gov. Romney how easy it is...
To Mittens: " Open Up or Drop Out " !! What are you hiding ?? Are you afraid to let the TRUTH be known ?? RELEASE Them and Let's Go Forward !!!!
I don't want to see his tax returns...I want to see his plans for healthcare, to create jobs, pay off our debt, fix our economy, ...oh wait that's right...he has no plans beside tax cuts for the top 1%.
Did anybody hear a denial of what Reid said in Romney's statement? Anybody?
Romney, you're the only one that can put up for shut up. It's obvious you haven't paid taxes before so you really shoul djust shut up.
I can't speak for everyone, but I am so tired of this kind of dirty politics. If it was a valid/true fact that Romney failed to follow the law with regards to his taxes then the head of the IRS should come out and say so. Otherwise, I really think both the news and the politicians should be solely focused on fixing the economy with the same energy they are showing for the dirty politics.
I think just all the way around Mitt Romney needs to put up and show the American public his tax returns like his dad did, Reagan did, Dole did, both Bush did, Obama did, Clinton did. Enough with his secret accounts in other countries and no taxes, he is running for president
Show us your taxes Mitt.... Oh there wasn't any, HA.
Romney loves telling the truth no matter how much liberals hate it! Shut up Harry! Romney 2012!
If Romney has nothing to hide, he should release more years of returns and prove it. Because right now I don't believe him.