Sunday.

The development came as Trump’s charge against Obama — leveled without any evidence — was being rebuffed both inside and outside of the executive branch. It drew a blunt, on-the-record denial by a top intelligence official who served in the Obama administration.

Speaking on NBC News on Sunday morning, former director of national intelligence James Clapper denied that a Foreign Intelligence Surveillance Act wiretap was authorized against Trump or the campaign during his tenure.

“There was no such wiretap activity mounted against the president-elect at the time as a candidate or against his campaign,” Clapper said on “Meet the Press,” adding that he would “absolutely” have been informed if the FBI had received a FISA warrant against either.

“I can deny it,” Clapper said emphatically.

In his claims early Saturday morning, the president tweeted that he “just found out” that Obama had “my ‘wires tapped’ in Trump Tower” before the election, comparing it to “McCarthyism.”

“Is it legal for a sitting President to be ‘wire tapping’ a race for president prior to an election?” Trump asked in another tweet. “Turned down by court earlier. A NEW LOW!”

By Sunday morning, the White House called for the congressional probe.

Current and former government officials said such surveillance would not have been approved by any senior Justice official in the Obama administration. And Trump’s allegation raised hackles in the FBI leadership, insinuating as it did that the bureau may have acted illegally to wiretap a presidential candidate without probable cause that he was an “agent of a foreign power,” as the foreign intelligence surveillance law requires.

“This is Nixon/Watergate,” Trump tweeted Saturday.

A spokesman for Obama countered several hours later that the former president never authorized a wiretap of Trump or any other American citizen. “Any suggestion otherwise is simply false,” the spokesman said.

White House press secretary Sean Spicer on Sunday cited “reports” of “potentially politically motivated investigations” during the 2016 campaign, calling them “troubling.” But none of the media reports cited by the White House provides evidence of a politically motivated surveillance effort against Trump.

“President Donald J. Trump is requesting that as part of their investigation into Russian activity, the congressional intelligence committees exercise their oversight authority to determine whether executive branch investigative powers were abused in 2016,” Spicer said.

“Neither the White House nor the President will comment further until such oversight is conducted.”

Congressional committees in both the House and the Senate are probing not just suspected Russian efforts to undermine the 2016 election but also any contacts between Russian officials and the Trump campaign.

Comey’s request is sure to raise eyebrows in light of his actions last year in the bureau’s investigation into Hillary Clinton’s email server.

Last July he held a news conference to announce that the bureau had concluded Clinton did not commit a prosecutable offense. Then, 11 days before the election, Comey wrote Congress despite warnings from senior Justice officials that doing so would violate department policy and said the FBI was examining new emails that had come to light. Nothing came of the bureau’s additional review, but Comey took heat for his actions, which Democrats say influenced the outcome of the election.

It is not clear why Comey, who is the senior-most law enforcement officer who has been overseeing the FBI investigation from its inception in the Obama administration, did not himself issue a statement to refute Trump’s claims. Nor is it clear to whom he made his request. Attorney General Jeff Sessions recused himself last week from all investigative matters related to the Trump campaign and any potential Russia links. The acting deputy attorney general, Dana Boente, a career federal prosecutor in the Eastern District of Virginia, is now overseeing the probe.

Trump’s tweets early Saturday may have been prompted by the comments of talk-radio host Mark Levin, which were summarized in an article on the conservative website Breitbart. The Breitbart story had been circulating among Trump’s senior aides on Friday.

The White House’s escalation of Trump’s claims were kept at arm’s length by congressional Republicans appearing on Sunday morning news broadcasts.

When asked about Trump’s allegations, Senate Intelligence Committee member Tom Cotton, an Arkansas Republican, declined to comment on the tweets but said he has “seen no evidence of the allegations.”

“Whether that’s a FISA court application or denial of that application or a re-submission of that application, that doesn’t mean that none of these things happened. It just means we haven’t seen that yet,” Cotton added, speaking on Fox News Sunday.

Sen. Marco Rubio, a Florida Republican, said he is not aware of evidence to back up the president’s claim. “I have no insight into exactly what he’s referring to,” he said on “Meet the Press.” “The president put that out there, and now the White House will have to answer for exactly what he was referring to.”

Obama’s allies were more blunt, denying flatly that the former president had ordered a wiretap of Trump’s campaign.

“This may come as a surprise to the current occupant of the Oval Office, but the president of the United States does not have the authority to unilaterally order the wiretapping of American citizens,” said former Obama White House press secretary Josh Earnest.

Senate Minority Leader Charles Schumer, a New York Democrat, told “Meet the Press” that Trump is “in trouble” and acting “beneath the dignity of the presidency.”

“The president’s in trouble if he falsely spread this kind of information,” Schumer said. “It shows this president doesn’t know how to conduct himself.”

Earnest added that Trump was attempting to distract from the controversy involving contacts between his campaign aides, including now-Attorney General Jeff Sessions, and Russian officials.

But appearing on ABCs “This Week,” White House Deputy Press Secretary Sarah Huckabee Sanders repeatedly said that the president’s allegation was worth looking into.

“He’s asking that we get down to the bottom of this, let’s get the truth here, let’s find out,” Huckabee Sanders said. “I think the bigger story isn’t who reported it, but is it true. And I think the American people have a right to know if this happened, because if it did, again, this is the largest abuse of power that, I think, we have ever seen.”

Asked whether Trump truly believes Obama wiretapped him, Huckabee Sanders deflected. “I would say that his tweet speaks for itself there,” she said.