Mitt Romney once again told Senate Majority Leader Harry Reid to "put up or shut up" about his taxes, telling Fox News Tuesday the Nevada senator had "lost a lot of credibility" with his claim about the candidate's taxes.

Reid told The Huffington Post last month that an anonymous Bain Capital investor said Romney paid no taxes for a decade. Romney denied the allegations and demanded to know where they came from, prompting a flurry of fact-check articles and statements from Republicans calling Reid's claims a lie.

"Well the message I gave Harry Reid was put up or shut up. I don't really believe that he’s got any kind of a credible source," Romney told Fox News on Tuesday. "I don’t know who gave him this line of reasoning, whether it came from the White House or the DNC or a staffer, but he ought to say where it came from and then we can find out whether that person has any credibility. I know they don’t because of course I paid."

Sean Spicer, the communications director for the Republican National Committee, questioned Monday whether President Barack Obama's campaign adviser, David Axelrod, was Reid's source, based on the mistaken idea that the senator made his claim after meeting with Axelrod. Although no one has been able to prove Reid's statement to be true, it also hasn't been proven false, and he and House Minority Leader Nancy Pelosi (D-Calif.) are standing behind it.

Romney said Democrats are simply trying to distract from their economic record.

“Well I think Harry Reid has lost a lot of credibility on a lot of fronts," he said. "This is just one more front that I think is a very unfortunate and sad course."

Also on HuffPost:

Loading Slideshow...
  • Ron Paul

    "Politically, I think that would help him," Paul said in a interview with <a href="http://www.politico.com/news/stories/0712/78599.html#ixzz20w7ycTBE" target="_hplink">Politico</a>. "In the scheme of things politically, you know, it looks like releasing tax returns is what the people want."

  • Richard Lugar

    "I have no idea on why he has restricted the number to this point," <a href="http://www.cbsnews.com/8301-18563_162-57474352/pressure-mounts-on-mitt-romney-to-release-more-tax-returns/?tag=socsh" target="_hplink">Lugar said</a>.

  • George Will

    "I don't know why... he didn't get all of this out and tidy up some of his offshore accounts and all the rest," Will said on ABC's "<a href="http://www.huffingtonpost.com/2012/07/15/george-will-mitt-romney-bain_n_1674513.html?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+HP%2FPolitics+(Politics+on+The+Huffington+Post)" target="_hplink">This Week</a>." "He's done nothing illegal, nothing unseemly, nothing improper, but lots that's impolitic."

  • Bill Kristol

    "He should release the tax returns tomorrow. It's crazy," Kristol said on "<a href="http://www.huffingtonpost.com/2012/07/15/mitt-romney-tax-returns_n_1674325.html" target="_hplink">Fox News Sunday</a>." "You gotta release six, eight, 10 years of back tax returns. Take the hit for a day or two."

  • Robert Bentley

    "I just believe in total transparency," Bentley told <a href="http://abcnews.go.com/blogs/politics/2012/07/gop-governor-calls-on-mitt-romney-to-release-additional-tax-returns-and-show-he-has-nothing-to-hide/" target="_hplink">ABC News</a>. "In fact, I was asked today that question -- do you think that Governor Romney should release his tax returns? And I said I do. I said, I release my tax returns. I may be the only public official in Alabama that does, but I release mine every year and I just believe that people should release their tax returns. And if you get them out and just get past that, it just makes it so much easier."

  • Haley Barbour

    When asked on "<a href="http://www.nationaljournal.com/2012-presidential-campaign/barbour-romney-should-release-more-tax-returns-20120710" target="_hplink">The Situation Room</a>" if Romney should release more returns, Barbour said, "I would. But should it be an issue in the campaign? I don't think it amounts to diddly."

  • Michael Steele

    "If there's nothing there, there's no 'there' there, don't create a there,'" Steele said on MSNBC.

  • David Frum

    "Tax returns the next problem. Releasing returns under pressure: more weakness, more pain," Frum <a href="https://twitter.com/davidfrum/status/224509505973661696" target="_hplink">tweeted</a>.