In mid-January, we urged Mitt Romney to release a passel of his old tax returns and let Americans read themselves blind. Those returns would, we expect, show what most of those Americans already know: The Republican presidential nominee-in-waiting has a fabulous income, donates great gobs of it to charity and -- because our tax code treats different sources of income differently -- he pays a lower effective federal tax rate than do many taxpayers who earn most of their money in wages.The most compelling reason for Romney to release returns last winter is just as compelling today: Multiple Congresses and presidents have spent the U.S. government gravely into debt. Tax policy -- including, we hope, a simplifying rewrite of the tax code -- can go a long way toward paying down that debt and reviving job creation. But if we're going to have a national debate on taxes, voters are entitled to know how a candidate has used the tax code and how various tax proposals would affect that candidate as a future president.

Had Romney obliged during the primary campaign, citizens would have had many months to explore his finances and factor them into their choice of the next president. Instead, Romney has released his 2010 return plus an estimate for his 2011 return. These documents confirm that Romney, like most Americans, legally takes advantage of whatever breaks the tax code permits. But they provide a very limited picture.

No law requires Romney to pay more than he owes, just as no law requires candidates to make tax records public. When he was being vetted as a potential vice presidential pick in 2008, Romney released 23 years of his returns to John McCain's campaign -- which isn't the same as making them public.

Democrats are free to bash Romney's reclusiveness. But bashing isn't enough to placate Harry Reid of Nevada, the Senate majority leader. Reid claims Romney went 10 years without paying taxes. Reid knows this because he heard it from an "extremely credible source" whom he won't identify, but who supposedly had invested with Romney's company, Bain Capital. What an investor in Romney's business would know about the Romney family's personal tax returns -- for 10 years -- is beyond our power to divine.

You don't need to even bicycle past the poli-sci department to understand Reid's gambit: Push voters to assume the worst, in the absence of real information.

Now we're in the zone of trying to prove negatives. Republican National Committee Chairman Reince Priebus didn't elevate the discussion when he offered Sunday that Reid is "a dirty liar." Nor did House Minority Leader Nancy Pelosi when she told the Huffington Post that "Harry Reid made a statement that is true. Somebody told him. It's a fact."

This sort of sophistry is rooted in nothing more noble than "whatever it takes for my side to win." Truth isn't the issue. Beating the other guy is. Even if it means prioritizing tactics so far above ethics that no accusation is beyond the pale. We weren't wrong July 22 when we knocked both campaigns for conducting "a race to the bottom." We erred only in not saying more about the irresponsible conduct of their surrogates.

Reid's unsupported tax allegation puts him squarely in league with "birthers" who question Obama's citizenship. That allegation hasn't stood up to scrutiny. Most birthers know this. They despise Obama so much, though, that the truth doesn't matter to them.

Which means Reid is, yes, a birther. Not because he refuses to believe Obama was born in Honolulu, as those 1961 birth announcements in the Honolulu Advertiser and Honolulu Star-Bulletin attest. No, Reid is a birther because he plays by birthers' rules. As Pelosi says, "it's a fact."

Someday, Reid will say something important that he genuinely wants Americans to believe. After this episode, they'll probably ignore him. We found ourselves nodding in agreement Monday with the opinion of Washington Post columnist Richard Cohen, no right-wing nut he: "The politics of this squabble are delightful. But Reid has managed to draw both his party and his president into the gutter with him. ... The soaring rhetoric that Obama used in his first campaign has come to ground in the mud of Harry Reid's latter-day McCarthyism."

The silver lining for Romney is that, just as Obama could prove the knuckleheaded birthers wrong, Romney can prove Birther Reid wrong.

Mr. Romney, one more time: Release your returns. If they show what you say -- that you "paid taxes every year. A lot of taxes" -- you'll get to watch Harry Reid try to convince voters that this was all a big misunderstanding.