In the long and storied history of congressional investigations, there’s no record of lawmakers acting at the president’s behest to get to the bottom of his own extraordinarily explosive but totally unsubstantiated allegations.

But that is going to be the case in the already amply unprecedented era of President Donald Trump. The result could not only change the very nature of legislative branch oversight, but also alter the turbulent course of this nascent administration.

Perhaps it was lip service, but maybe not. Either way, the Republican chairmen of the Intelligence committees in both the House and Senate have committed themselves to the same promise: They will honor the president’s request and investigate his claim that his predecessor Barack Obama overstepped his presidential authority and ordered the wiretapping of Trump’s telephones during last year’s campaign.

And top Democrats on those panels are saying, in effect, bring it on — sounding confident they will be able to extract overwhelming evidence portraying Trump as the fabricator in chief, maybe as soon as a televised hearing a week from Monday.

While an incumbent president bugging the offices of a would-be successor would be a historic scandal, “that is also a scandal if those allegations prove to be false,” Adam Schiff of California, the ranking Democrat of House Intelligence, told reporters Tuesday night. “And we should be able to determine in fairly short order whether this accusation was true or false.”

The two Intelligence committees are already taking the lead for Congress in investigating Russia’s efforts to interfere in the election and tip the outcome Trump’s way.  For those same panels to start an inquiry into Trump’s phone-tapping accusation is a clear sign lawmakers assume that, if there was any surveillance of Trump Tower last fall, it was somehow connected to the Russians’ meddling.

“All of that is part of the same investigation,” Senate GOP Whip John Cornyn of Texas, a member of the Intelligence Committee, said Tuesday when asked why the panel was looking at the wiretapping allegation.

Reports that Trump and his campaign officials were being investigated by federal law enforcement agencies on suspicion of collaborating with the Russians were already of interest to the House Intelligence panel before Trump asked for a congressional inquiry, the panel’s chairman, California Republican Devin Nunes, told reporters the same day.

Through different prisms

Those crisp syntheses underscore how Trump’s own partisan allies on the Hill view the situation fundamentally differently from him. Circumstantial evidence and his own behavior patterns suggest the president leveled the phone-tapping charge at least in part hoping to divert attention from the Russia issue. The accusations were aimed directly at his predecessor in a series of tweets Saturday, just hours after widespread reports he’d erupted in anger at a West Wing staff meeting because presidential coverage remains so dominated by Russia.

Neither he nor anyone at the White House has offered any evidence to support the claim, although he has the authority to disclose how he “just found out that Obama had my ‘wires tapped’ in Trump Tower just before the victory,” as his initial tweet alleged at 6:35 a.m. (The second follow-up, complete with misspelling 27 minutes later, said: “How low has President Obama gone to tapp my phones during the very sacred election process. This is Nixon/Watergate. Bad (or sick) guy!”)

The allegation is sufficiently incendiary that Nunes and his Senate counterpart, Richard M. Burr of North Carolina, would be hard-pressed to avoid expressing some interest in following up — even though both concede they have not seen any evidence to back up the claim.

But the obvious risk — for the president much more than for congressional Republicans — is that by making sure their inquiries are sustained and serious, the chairmen could set in motion a definitive refutation of Trump’s charges.

Potential blowback

There’s no polling on the matter yet, of course, but it’s not unreasonable to predict that plenty of voters who are currently part of Trump’s loyal GOP base will start viewing him less fondly if his own fellow Republicans on the Hill conclude he acted irresponsibly and demeaned the presidency itself by falsely accusing his predecessor of an impeachable offense. (The notion that Trump may have tweeted imprecisely because he’s “a neophyte to politics,” which Nunes test-marketed this week, is not likely to stand the test of time.)

Democrats have more ability to push the Republicans into this corner than many in the public may understand.  The two Intelligence committees have deserved reputations as relative oases of two-party collaboration in a Capitol beset by partisan rancor.

They do not normally operate in ways that give the majority the overwhelming amount of leverage to make the rules and decide the priorities, as all the legislative committees do. By custom if not quite dictate, authority to direct staff investigators, arrange hearings and issue subpoenas is shared by the Democrats and Republicans no matter which party has a couple of extra members on the dais.

And so it was with a bipartisan stamp of approval that the House panel unveiled the roster of former and current senior officials invited to be witnesses at a potential blockbuster hearing March 20: The headliners look to be James R. Clapper Jr., who was director of national intelligence at the end of the Obama administration and has declared there was no Foreign Intelligence Surveillance Act, or FISA, request to wiretap Trump; and FBI Director James B. Comey, who reportedly pressed the Justice Department to repudiate  Trump’s claim.

Others invited are National Security Agency Director Michael S. Rogers, former CIA director John Brennan, former acting Attorney General Sally Yates and two top officers of the cybersecurity firm that found proof of Russian hacking of the Democratic National Committee.

The televised tableau of Comey, Clapper and maybe others flatly contradicting Trump would be the most extraordinary rebuff to a president’s veracity and trustworthiness in almost two decades. And it would be on a question more fundamentally meaningful to the American system of government than in 1999, when Bill Clinton defended himself in an impeachment trial for allegedly committing perjury and obstructing justice while seeking to conceal a sexual relationship with a White House intern.

Even if Congress is unable to definitively contradict Trump’s charges, the Hill inquiries he’s requested carry other risks for the president.

At a minimum, they will keep Russia’s involvement in the campaign in the public eye longer than the president wants, complicating the selling of his legislative agenda.

And, if the Intelligence committees unearth damaging personal or financial information about him, or expose shady dealings by his campaign organization and its leaders, the Democrats will have access to all that information and could wield it against the president or whomever they choose.