Yet the White House communications office, likely sensing that the tweets were in danger of blowing up in its face, issued a statement last week saying it would not comment but that Trump wanted Congress to investigate. (Various members of Trump’s circle have studiously avoided putting too much of their own credibility behind the accusation.)

There were, from the start, a series of problems with the accusation. For example, Trump offered no evidence for any of them. For another, they corresponded neatly in time with a Breitbart story that made similar accusations, also without evidence; that story followed comments from right-wing radio host Mark Levin, who also made similar accusations, also without evidence.

Somehow, despite the utter lack of substantiation, the story continues to roll on. The White House has made one minor concession, claiming—semi-plausibly—that Trump did not mean a literal wire tap, but simply meant the Obama administration had been surveilling him somehow.

In an interview with Tucker Carlson on Wednesday, Trump tried to explain that wiretapping could mean many things.

“That really covers surveillance and many other things,” he said. “Nobody ever talks about the fact that [‘wire tap’] was in quotes, but that’s a very important thing.”

For reasons that escape this observer, this question of vocabulary has become a major part of the story, even though it appears to be a wholly irrelevant semantic discussion. One could go back through Trump’s tweets and look for proof that his use of quotation marks in the tweets shows he didn’t really mean what he said. (Brad Jaffy of NBC News has, in fact, done this yeoman’s service.) But why bother? If Obama improperly or illegally surveilled Trump, surely the method does not matter.

Indeed, Trump stuck to the fundamental accusation against Obama during his conversation with Carlson, saying he would send some new information to congressional investigators. “You’re going to find some very interesting items coming to the forefront over the next two weeks,” Trump said. During a hectic press briefing on Thursday, White House Press Secretary Sean Spicer said of the allegation, “He stands by it.”

Spicer’s task in defending Trump was a little more difficult because earlier Thursday, Senators Richard Burr and Mark Warner—the chair and ranking member, respectively, of the Senate Select Committee on Intelligence—had issued a statement casting doubt on the claim.

“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 senators said.

House Intelligence Committee Chair Devin Nunes had previously said he had seen no evidence of a wiretap, but the Burr-Warner statement is notable because of its breadth, saying that they saw no indications of any surveillance of any type.