(CBS News) Refusing to retreat from his allegations that Mitt Romney hasn't paid taxes in 10 years, Senate Majority Leader Harry Reid, D-Nev., on Thursday night argued his claim comes from "an extremely credible source," and said he believes the presumptive GOP presidential nominee's personal wealth might be playing a role in helping him evade the law.
"People who make as much money as Mitt Romney have many tricks at their disposal to avoid paying taxes," Reid said in a statement. "Last weekend, Governor Romney promised that he would check his tax returns and let the American people know whether he ever paid a rate lower than 13.9 percent. One day later, his campaign raced to say he had no intention of putting out any further information."
(Watch: Reid's remarks Thursday.)
Romney has released one year of tax returns and an estimate for another, but has come under fire from President Obama's campaign and other Democrats for not returning more, particularly considering the heft of his wealth and hazy investment in offshore accounts. Reid argued "when you're running for president, you should be an open book," and said it's Romney's "obligation to put up, and release, several years' worth of tax returns just like nominees of both parties have done for decades."
Following Reid's initial charge on the Senate floor Thursday, Romneythe majority leader's comments as "baloney" on conservative host Sean Hannity's radio show, advising Reid to "put up or shut up" about the identity of his anonymous source.
(Watch: Romney says he pays "a lot of taxes" every year.)Some political watchdogs are backing Romney's call for Reid to fess up, citing his accusation as irresponsible hearsay. Others are critical of Reid for not having released his own tax returns; Reid defends himself by arguing the bar for disclosure is higher when you're running for president.
But Reid claimed only one way for Romney to dodge further scrutiny on the issue, "and that's release his tax returns," he said. "It's clear Romney is hiding something, and the American people deserve to know what it is."
**CORRECTION: A previous version of this story stated that Romney released two years of tax returns as required by law. He has released one (and one estimate), which is not required of presidential candidates.