IT WAS almost as if Donald Trump was taunting his Republican colleagues. After tweeting an explosive and wholly unsubstantiated claim against Barack Obama on March 4th—“How low has President Obama gone to tapp [sic] my phones…Bad (or sick) guy!”— the president said it was up to Congress to investigate the matter. “Neither the White House nor the president will comment further,” primly declared his spokesman, Sean Spicer, “until such oversight is conducted.”

Some sort of follow-up is necessary. Mr Trump is the president, 47% of Americans trust him more than they trust the media (according to a Quinnipiac poll), and his charge against Mr Obama was grave. If it were shown that his administration illegally snooped on Mr Trump, Mr Obama’s legacy would be disgraced. Alternatively, if it secured a warrant to bug Mr Trump’s phones, that would mean it had sufficient cause to believe Mr Trump or his associates were involved with terrorists or foreign spies to convince a judge on the Foreign Intelligence Surveillance Court. On the other hand, if Mr Trump, an inveterate conspiracy theorist, was peddling inflammatory nonsense about his predecessor and America’s intelligence agencies, that would also be serious. And it is probably the case.

Mr Obama’s director of national intelligence, James Clapper, said there was no warrant against Mr Trump. James Comey, the head of the FBI, upset that the president appears to have accused his agency of a serious crime, reportedly asked the Justice Department to repudiate his claim outright. Mr Trump’s aides have meanwhile put up such a valiant but hapless defence of it that, if the issue were not so serious, it would be comical. Asked why Mr Trump wanted Congress to investigate a crime the president claimed to have proof of, Mr Spicer lost the power of spin. It was because of the “separation of powers”, he fluffed. It would be good, he explained, to get Congress “as a separate body to look into something, and add credibility to the look, adds an element that wouldn’t necessarily be there.”

Mr Trump, who launched his political career by claiming Mr Obama was born in Africa and last year suggested the father of his main Republican rival had a role in the murder of John. F. Kennedy, appears to have based his claims on a rant by a talk-radio host, Mark Levin, which was reported on Breitbart News, a Trumpish website. To support the president’s contention, White House aides referred to Breitbart and to separate reports, by the BBC and others, that the FBI had obtained a warrant to investigate individuals linked to the Trump campaign over their Russia ties. None of the reports mentioned wiretapping.

Mr Trump’s motive for turning these unproven scraps into perhaps the most serious charge by a serving president against his predecessor appears straightforward, given his history. He is enraged by suspicions that his campaign was, to some degree, in cahoots with Russians who—in the view of America’s intelligence agencies—interfered with the election. The latest piece of circumstantial evidence came on March 2nd, when it was revealed that Mr Trump’s attorney-general, Jeff Sessions, had twice met with the Russian ambassador to Washington, Sergey Kislyak, during the campaign, despite denying during his Senate confirmation hearing having had “communications with the Russians”. Mr Sessions recused himself from any investigation touching on the campaign—which would include an ongoing FBI probe into Russia’s role in the election—even though Mr Trump had said he should not make such a concession. By smearing Mr Obama, the president may have hoped not only to deflect attention from talk of Russia, but also to arm his supporters with a made-up counter-scandal to set against it.

Warp-speed

Many Republicans are alarmed by Mr Trump’s latest haymaker against Mr Obama. His half-dozen somewhat vocal critics, who are mostly senators and include moderates such as Susan Collins of Maine, old warhorses such as John McCain of Arizona, and, in Ben Sasse of Nebraska, a principled conservative, have politely cast doubt on Mr Trump’s allegations. “We are in the midst of a civilisation-warping crisis of public trust, and the president’s allegations today demand the thorough and dispassionate attention of serious patriots,” wrote Mr Sasse. There are also signs that shyer critics of Mr Trump may be, if not breaking ranks, at least emitting distress signals. “I’ve got to believe—I think he might have something there, but if not, we’re going to find out,” said Representative Jason Chaffetz of Utah when asked about the president’s allegations.

Together with Mr Sessions’s embarrassment, the episode has at least increased the pressure on the House and Senate intelligence committees to pursue seriously the investigations each has launched into Russia’s meddling. Both are in the process of launching their inquiries. The House committee agreed on the scope of its investigation last week; most members of the Senate committee, including the Republican chairman, Richard Burr of North Carolina, and the ranking Democrat, Mark Warner of Virginia, were due in Langley to receive a preliminary CIA briefing this week. Yet there are doubts about how zealously the committee’s Republican members will quest for the truth.

It was recently revealed that Mr Burr and his counterpart in the House committee, Devin Nunes, a Republican from California, were both asked by the administration to try to convince journalists that there was no incriminating link between the Trump campaign and Russia—a surreptitious arrangement that made a mockery of Congress’s responsibility to hold the executive to account. The House committee seems unlikely to pursue its task with great diligence. Mr Nunes, has suggested that what needs investigating is the leaks to journalists that have embarrassed the White House, a nod to an idea newly popular among the president’s most ardent supporters that a “deep state” is thwarting a democratically elected leader, a conspiratorial notion borrowed from semi-democracies that casts Mr Trump as a victim.

There is greater hope for the Senate committee, which has a history of bipartisanship and includes several independent-minded Republicans, including Ms Collins. “We are going to have unprecedented access to all the intelligence,” said Mr Warner. “I am confident we’re going to find out the truth.”

The trouble is, the committee may be bipartisan, but America is not—and therein lies Mr Trump’s abiding opportunity. Though his approval ratings are poor generally, among Republicans they are dandy. Any Republican who defies the president therefore risks serious damage to his career—so most will not.