Top Republicans have spent days distancing themselves from President Donald Trump’s unsubstantiated allegation that President Barack Obama tapped his phones. Now the heads of the Senate Intelligence Committee are flatly saying it didn't happen.

“Based on the information available to us, we see no indications that Trump Tower was the subject of surveillance by any element of the United States government either before or after Election Day 2016," the panel’s chair, Republican Sen. Richard Burr, and ranking member, Democratic Sen. Mark Warner, said in a joint statement.

The unusually definitive public comments from the heads of the Senate intelligence panel come one day after Trump offered a rambling and largely incoherent defense of his claim about the wiretap, one of the most explosive allegations in recent American political history. Pressed to substantiate it during an interview with Fox News host Tucker Carlson, the president said this:

Well, I've been reading about things. I read in, I think it was January 20, a New York Times article where they were talking about wiretapping. There was an article, I think they used that exact term. I read other things. I watched your friend Bret Baier the day previous where he was talking about certain very complex sets of things happening, and wiretapping. I said, “Wait a minute; there's a lot of wiretapping being talked about.” I've been seeing a lot of things.

Trump had already been largely alone in trying to defend the allegation, which had been angrily denied by both Obama himself and former aides such as James Clapper, who was the nation’s top spy during the previous administration.

On Wednesday, House Intelligence Committee Chair Devin Nunes — a devoted Trump ally and defender — flatly said that “clearly the president was wrong” if you take his tweets about Obama’s wiretapping “literally.”

“I don’t think there was an actual tap of Trump Tower,” Nunes said.

Next, embattled Attorney General Jeff Sessions, already under fire for misleading a Senate committee about his contacts with the Russian ambassador to the US, pushed back at his own boss when a reporter asked if he’d ever given Trump “reason to believe that he was wiretapped by the previous administration.”

In a third blow, Republican Sen. Chuck Grassley, a veteran GOP lawmaker and chair of the Senate Judiciary Committee, said he would block Trump’s pick for deputy attorney general, Rod Rosenstein, unless the FBI explicitly answered his panel’s questions about Trump’s claims.

Regardless of whether the Justice Department leadership complies, FBI Director James Comey — who has already made clear that he wants senior Justice Department officials to publicly repudiate Trump’s claim — will get the chance to do so himself next week when he testifies at a high-profile hearing about Russia’s interference in the presidential election.

Democrats are likely to push Comey to say explicitly that Trump made the entire thing up, a statement that would mean the FBI chief was accusing his own boss of lying. The Burr-Warner statement might make it easier for Comey to navigate that political minefield.

Pity the White House communications staff who have to defend an imaginary accusation

Even before the statement from Burr and Warner saying there was no evidence to support Trump’s claim, the allegation had been unraveling for so long that it was easy to lose sight of the fact that no Republicans of any stature had been willing to defend it — and that even Trump’s closest aides had been twisting themselves into pretzels to avoid having to explicitly concede that their boss seems to have made the entire thing up.

In the past few days alone, White House spokesperson Sean Spicer used actual air quotes to suggest Trump hadn’t literally been talking about wiretapping even though the president’s own tweets had literally been talking about wiretapping, while Trump adviser Kellyanne Conway hinted that the real culprits were tiny cameras hidden inside microwave ovens. (That statement prompted this gem of a sentence from the New York Times: “Ms. Conway clarified on Monday that she was not accusing the former president of snooping via a kitchen appliance.”)

Trump’s charge became harder and harder to defend as aides continued to be unable to provide any evidence to back it up, and as the Washington Post reported that the allegation seemed to originate with an unsourced Breitbart article circulating among top Trump aides titled “Mark Levin to Congress: Investigate Obama’s ‘Silent Coup’ vs. Trump.”

Now, fewer than two weeks after Trump roiled the political world with the charge, it has been knocked down by one of the few lawmakers in a position to definitively say whether or not it had happened. Trump, in other words, has members of his own party effectively saying he made the entire thing up.