FOR the dwindling few out there who still believe that big accusations require a little foundation and that truth — as opposed to conjecture — matters, here’s an update:

As last week drew to a close, Harry Reid, the Senate’s Democratic majority leader, had backed up his claim that Mitt Romney didn’t pay taxes for a 10-year period with absolutely nothing more than some vague reference to some unnamed guy who said something of the sort to Reid during some phone conversation some time ago.

That’s it. That’s all. But for Reid, it was enough not only to level his charge but also, as the days pressed on, to double and triple down on it, his language and manner growing more righteous even as his evidence grew no more detailed or persuasive.
The claim appeared first in an interview with The Huffington Post that went online Tuesday.

“Now, do I know that that’s true?” Reid said in the interview, which also included his mention of the phone call, supposedly from an investor in Bain Capital. “Well, I’m not certain.”
No biggie! Full steam ahead! He proceeded to assert that Romney’s net worth is probably greater than published estimates of $250 million because, he explained, “You do pretty well if you don’t pay taxes for 10 years.” And so a wild supposition was magically transformed into the given from which yet another bit of speculation blossomed, and any concern with provable information was long gone, a casualty of the craven rules of political engagement these days. It’s beginning to seem as if everyone’s at the prow of a Swift Boat, pants on fire and conscience on ice.
Spew first and sweat the details later, or never. Speak loosely and carry a stick-thin collection of backup materials, or none at all. That’s the M.O. of the moment, familiar from the past but in particularly galling and profuse flower of late.

It has spread beyond the practiced rabble-rousers of the far right, and Democrats are exuberantly getting in on this unbecoming, corrosive game. For many years they bemoaned an unfair fight: Republicans were by and large willing to play faster, looser and flat-out nastier than they were. Is there as much credibility to that lament today?

The Democratic Congressional Campaign Committee was forced last week to issue a public apology to the international casino magnate Sheldon Adelson, who is giving tens of millions to Republicans this year, for having asserted on its Web site that he was knowingly profiting from “a Chinese prostitution strategy” at his casino in Macau. It has no proof of that.

Its defenders will say that Adelson is so brazenly exploiting lax campaign-finance regulations to hijack the political process that he must be discredited and neutralized by whatever means necessary. Details, schmetails.

And Reid’s defenders will say that Romney’s reluctance to release more than one complete year of tax returns (at least so far) makes clear that he’s hiding something, which must be flushed out one way or another. Plus, to them, Reid’s claim has the feel of near-truth. It passes muster as a metaphor if not as a matter of demonstrable fact. It’s a genuinely felt worry of sorts and valid as such.

But if you’re going to subscribe to that sort of reasoning, “You might as well put a dead cocker spaniel on your head and start yelling about birth certificates,” said Jon Stewart on “The Daily Show,” flashing a photograph of the quizzically coiffed Donald Trump, who to my eyes was wearing either an Irish setter or maybe a Pomeranian. Stewart’s point — an excellent one — is that the crazies who insist that President Obama wasn’t born in the United States are Reid’s philosophical and strategic kinfolk.

DO one tribe’s antics justify the other’s? Is this a road we really want to continue barreling down? We’re already on it, thanks in part to a presidential contest in which each candidate’s main pitch — I’m not half as awful as the other guy — points everything in a negative direction.

The new shape of the news-media universe doesn’t help. Balkanized into micro-niches where partisans can have their passions stoked and prejudices reinforced, it gives reckless allegations many places to land and even stick before they get a sober look. Those allegations are intended and tailored to rally the troops, who are believed to care more about truculence than truthfulness. The ends justify the Reid.

After the Senate leader made his accusation, the Salon.com writer Alex Seitz-Wald consulted several tax attorneys about its theoretical plausibility and determined that it was “nothing short of ludicrous.” Meanwhile, the Romney campaign — and, later, Romney himself — denied the charge.

Reid was unbowed. Inconsistent, too. At one point he told reporters from his home state of Nevada that “a number of people” had whispered to him of Romney’s alleged tax evasion, while at a subsequent point he issued a statement citing only “an extremely credible source,” singular. In neither instance did he hang any flesh on these bones.

“I don’t think the burden should be on me,” said Reid, whose history of intemperate, borderline adolescent remarks was detailed in The Times by Michael D. Shear and Richard A. Oppel Jr. “The burden should be on him. He’s the one I’ve alleged has not paid any taxes.”

So if I just decide to allege that Reid levied that accusation under detailed and persistent instructions from the Obama campaign, the burden would be on him to provide all of his office’s e-mail and phone correspondence in order to contradict that?

Reid took a wholly legitimate source of concern — that Romney owes voters more candor and transparency than he has been willing to furnish — and undermined it by going too far and too farcical.
But then there’s plenty of overreaching tragicomedy to go around.

“Sometimes I have to catch my breath and slow down because the rhetoric in this campaign is just over the top,” observed John Boehner, the Republican speaker of the House, on the Fox News Radio show “Kilmeade and Friends” on Thursday. In regard to Reid’s casual slander of Romney, Boehner said, “It’s one of the problems that occurs here in Washington. People run out there without any facts and just make noise.”

And in that very same interview, when Boehner turned his attention to President Obama and called him inept at creating jobs, he also said: “He’s never even had a real job, for God’s sake.” Thus he made his own journey over the top, facts falling by the wayside, his pants getting toasty, the noise grinding on and on.