Senate Majority Leader Harry Reid (D-Nev.) has got the goods on Mitt Romney — or so he claims. Reid says that an unidentified investor in Bain Capital, Romney's former company, once told him that Romney had not paid any taxes over a 10-year stretch, instead socking his money away in tax havens in the Cayman Islands and Switzerland. Romney vigorously denies the charge, and has slammed Reid for not providing any proof, challenging him to either "put up or shut up." Meanwhile, commentators from across the political spectrum are criticizing Reid's seemingly baseless accusation, with the liberal comedian Jon Stewart calling Reid out for taking a "bullshit shot." But still, Reid is sticking like glue to his guilty-until-proven-innocent stance, saying Romney could clear this up by releasing more than two years of tax returns, which Romney has refused to do. Will Reid regret his attack over Romney's taxes?

Yes. Reid is probably lying: "Shame on [the] gossipy gentleman from Nevada," says Dan Primack at CNN. His claim that the info came from a Bain investor doesn't even add up: "Investors in private equity funds do not receive, nor are they entitled to request, personal tax returns for fund managers" like Romney. The Republican's tax returns probably weren't even "prepared or reviewed in the firm's offices," so how could an investor know the details? Either Reid is lying, or his supposed "source" is "full of it."

"Calling BS on Reid's Bain tax claims"

And this will further damage Reid's reputation: It's "no surprise that Reid would smear Romney so casually," says Allahpundit at Hot Air. Reid specializes in baseless attacks — in 2008 he "made more noise about [John] McCain's temper being a sign of possible derangement than any other major Democrat." Reid is an "unusually nasty character, even by normal political standards," and he's disgracing his office by spreading the sort of eye-roll-worthy rumors that birthers specialize in.

"Harry Reid: This might not be true, but some Bain investor who I won't name told me Romney didn't pay income taxes for 10 years"

But Reid is successfully keeping Romney's taxes in the spotlight: Sure, "Reid's accusation does sound too extreme to be true," says Caroline Bankoff at New York. But he's "not backing down," because even wild slander will ensure that voters continue "asking why Romney is so committed to keeping his tax returns under wraps." It's guaranteed that "these stories are going to keep coming, because for Romney's political enemies, it's just too easy."

"Mitt Romney responds to claim that he didn't pay taxes for a decade"

Read more political coverage at The Week's 2012 Election Center.