For the past four years, various Republican officials have speculated that Barack Obama might be the foreign-born perpetrator of an elaborate biographical hoax, and thus not a legitimate president. Among them were several senators, including Oklahoma’s Jim Inhofe, who was quoted in Politico saying that the birthers “have a point.” Later, in a statement, he added, “The White House has not done a very good job of dispelling the concerns of these citizens.”

More recently, several Republican congressmen, led by Michele Bachmann, have demanded an investigation into Muslim Brotherhood infiltration into the Obama administration. While some in the party have denounced her, Mitt Romney adviser John Bolton came to her defense, asking, “What is wrong with raising the question?”

Yet somehow, after years in which calumnies against the president and his administration have become so routine as to be unremarkable, Harry Reid’s suggestion that Romney might have avoided paying taxes has roused establishment pundits to fits of pearl-clutching horror. On Sunday’s This Week With George Stephanopoulos, ABC News’s Jonathan Karl called Reid’s statements "one of the most outrageous charges that I've ever seen actually made on the Senate floor.” On Face the Nation, Bob Schieffer compared Reid’s charges with McCarthyism, an analogy that The Washington Post’s Richard Cohen reported on Monday: “The soaring rhetoric that Obama used in his first campaign has come to ground in the mud of Harry Reid’s latter-day McCarthyism.” On Tuesday, the Chicago Tribune ran an editorial headlined, “Harry Reid, Birther.”

Now simply claiming that the other side is worse is not a defense against political wrongdoing, and journalists needn’t judge ethical lapses on a curve. Still, Reid’s insinuations are pretty tame by the standards of contemporary political combat. The idea that Obama has camouflaged his past in order to illegally usurp the presidency requires wild leaps of logic and, if true, would mean that he is a criminal. The same is true of the frequent Republican allegations that Bill Clinton had Vince Foster murdered. By contrast, every year more than a thousand millionaires use various legal accounting tricks to avoid paying income taxes. Reid’s claim is not incredible on its face, nor does it imply that Romney has broken any law.

This is not to say that Reid is playing entirely fair, just that he’s engaged in ordinary politics, not some outrageous new breech of decorum. The McCarthy analogy is particularly absurd. McCarthy’s wild accusations were poisonous for two reasons. First, they often relied on guilt by association—peoples’ lives were destroyed simply for associating with those deemed unsavory. Second, they were almost impossible to disprove. By contrast, if Reid is lying, it would be easy enough for Romney to discredit him. (And no journalist who has ever quoted an anonymous source should automatically assume that he is.)

That why the birther comparison is ridiculous as well. Obama released his birth certificate, but Republicans insisted on insinuating that it was a fake. For the birther analogy to make sense, Romney would have to release his tax returns, and Democrats would have to accuse him of forging them. But Romney, to the bafflement of many in his own party, is breaking with a campaign tradition established by his own father and keeping his returns secret. He is demonstrably hiding something. It is not beyond the pale for political players to speculate about what that is.

What really seems to be going on here is that a Democrat is successfully engaged in the sort of hardball tactics that Republicans usually have a monopoly on, and the media don’t quite know what to make of it. When it comes to making wild, unsubstantiated allegations, the GOP benefits from the soft bigotry of low expectations—at this point, few people can bring themselves to get that worked up about insane Republican mudslinging. Yet when a Democrat even tiptoes in that direction it’s news, and a chance for pundits to demonstrate the bipartisan bona fides so valued in the Beltway. It’s not balance, though, to equate the toughest rhetoric coming from each side when they’re saying such radically different things.