White House press secretary Sean Spicer refused Monday to explain President Donald Trump’s explosive allegation that his predecessor, former President Barack Obama, had ordered surveillance against him.

Spicer wouldn’t say if Trump had personally seen evidence of the claim, or if he had based the accusation entirely on a talk-radio segment and a story published by Brietbart News, the conservative website once run by his chief strategist, Stephen Bannon. Spicer wouldn’t say if Trump was accusing his predecessor of breaking the law. And he wouldn’t say if Trump would accept the results of a congressional investigation he’s requested into his unfounded claim.

“I’m just going to let the tweet speak for itself,” Spicer said.

But even as he refused to offer evidence backing the allegation, Spicer doubled down on Trump’s claim, saying there was “no question that something happened.”

“The question is, is it surveillance, is it a wiretap, or whatever,” Spicer said.

Early Saturday Trump issued a series of remarkable tweets claiming that he had “just found out that Obama had my ‘wires tapped’ in Trump Tower just before the victory.” Trump later went on to specifically accuse Obama of tapping his phones.

A spokesman for Obama issued a statement denying the charge, saying the president had never ordered surveillance on any U.S. citizen. And former U.S. intelligence officials disputed the allegations over the weekend.

“I can deny it,” James Clapper, the Obama administration’s director of National Intelligence, said Sunday on NBC’s “Meet the Press” when asked whether he could confirm or deny that a court order existed allowing for eavesdropping at Trump Tower in New York.

Joining Clapper in knocking down Trump’s assertions — although not publicly — was FBI Director James Comey, who asked Justice Department officials to issue a statement rejecting Trump’s claims, according to a U.S. official who requested anonymity to discuss sensitive issues. The department hasn’t done so. The New York Times first reported Comey’s request.

Spicer refused to answer questions about Comey’s assertion, saying reporting of the FBI director’s concerns was based on anonymous sources. Spicer said he didn’t believe Trump and Comey had spoken since the president’s tweets.

“If we start down the rabbit hole of discussing some of this stuff, I think then we end up in a very difficult place,” Spicer said.

A former director of the Central Intelligence Agency and the National Security Agency during the George W. Bush administration, retired Air Force Gen. Michael Hayden, said Monday that a president can’t order such wiretapping and that “to set the record straight” secret court records may need to be provided to Trump in an “unprecedented” move.

There are other ways for Trump to determine the truth, he said. “It looks as if the president just for a moment forgot that he was president,” Hayden told Fox News. “Why didn’t he simply use the powers of the presidency to ask the acting director of national intelligence, the head of the FBI to confirm or deny the story he apparently read from Breitbart the evening before?”

Trump’s claims relied on reports in conservative media, including Breitbart News, a person familiar with the situation told Bloomberg News.

“Let’s get to the bottom of it. That is the president’s entire point,” Trump adviser Kellyanne Conway told Fox News on Monday without providing evidence of the wiretapping claims. “He has intelligence and information that the rest of us do not.”

On Sunday, Spicer called on Congress to investigate the reports. Democrats said the White House was trying to shift the focus away from investigations into possible connections between the Trump campaign and Russia. Trump’s allegations came two days after the top U.S. law enforcement officer, Attorney General Jeff Sessions, recused himself from investigations of Russian interference with the election, including Russian contacts with associates of Trump related to the campaign.

“There is one page in the Trump White House crisis-management playbook,” former Obama press secretary Josh Earnest said on ABC’s “This Week.” “And that is simply to tweet or say something outrageous to distract from a scandal.”

Senate Intelligence Committee Chairman Richard Burr, R-North Carolina, said in a statement that the panel “will follow the evidence where it leads, and we will continue to be guided by the intelligence and facts as we compile our findings.”

Trump was furious about the recusal by Sessions — a decision the attorney general came to on his own — because it made the administration look weak, said a person familiar with the situation. On Friday, the president yelled at senior staff in the Oval Office, an incident witnessed from a distance by reporters with zoom-lens cameras waiting outside the White House for Trump to board his Marine One helicopter for Joint Base Andrews and a weekend in Florida.

In his tweets, the president described the alleged wiretapping as a “Nixon/Watergate” process, and called Obama a “bad (or sick) guy.”

In a statement issued the next day, Spicer said 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.”

Neither the White House nor the president will comment further “until such oversight is conducted,” Spicer said.

Clapper said he would “absolutely” have known if a Foreign Intelligence Surveillance Act court order had been approved to spy on Trump’s home and office complex. “To my knowledge” there was no such order of anything at Trump Tower, he said.

“For the part of the national security apparatus that I oversaw as DNI, there was no such wiretap activity mounted against the president-elect at the time or as a candidate or against his campaign,” Clapper said.

The DNI, the top intelligence official in the U.S. government, oversees the intelligence efforts of more than a dozen civilian and military agencies. “I can’t speak for other authorized entities in the government or a state or local entity,” Clapper said.

Hayden said “it would be really unprecedented” to provide classified records from the FISA court — which must approve surveillance of Americans in intelligence investigations — to a sitting president, but “we’re off the map here. We are in unprecedented territory as well, so perhaps at some point in order to set the record straight we may do something unusual.”

Tom Cotton, R-Arkansas, a member of the Senate Intelligence Committee, said on “Fox News Sunday” that the matter will be part of its ongoing inquiry. Asked whether he’s seen any evidence that the Obama administration wiretapped Trump Tower, Cotton said, “I’ve seen no evidence of the allegations we’ve seen in the media.”

Rep. Devin Nunes of California, the Republican chairman of the House Intelligence Committee, also said in a statement on Sunday that his panel “will make inquiries into whether the government was conducting surveillance activities on any political party’s campaign officials or surrogates, and we will continue to investigate this issue if the evidence warrants it.”

Sen. Marco Rubio of Florida, a member of the Senate Intelligence Committee, said on CNN’s “State of the Union” that if Trump’s allegations aren’t true, “then, obviously, he’ll have to explain what he meant.”

Democrats phrased their comments with care. “I am not aware of any FISA court order regarding Trump Tower,” Sen. Mark Warner said on CBS’ “Face the Nation.”

The Virginia lawmaker, the top Democrat on the intelligence panel, left open the possibility of a FISA order or other surveillance directed outside of Trump Tower or the Trump campaign.

House Democratic leader Nancy Pelosi, speaking on CNN, said Trump’s contentions about Obama, and the call for a congressional inquiry, were an attempt at deflection. “Rather than Russia, we’re talking about, did President Obama do thus-and-so,” she said.

“It’s called a wrap-up smear,” the California Democrat said of the wiretapping claims. “You make up something. Then you have the press write about it. And then you say, everybody is writing about this charge. It’s a tool of an authoritarian.”

Chuck Schumer of New York, the top Senate Democrat, continued to demand that a special prosecutor be named to look into the Trump campaign’s Russian activity.

Leon Panetta, a former secretary of defense and director of the Central Intelligence Agency under Obama, said Trump’s unproven accusations send “a terrible message” to other countries. “It makes us vulnerable to our enemies,” Panetta said on CBS.

That sentiment was echoed by Rep. Adam Schiff of California, the top Democrat on the House intelligence committee. “For a president of the United States to make such an incendiary charge — and one that discredits our democracy in the eyes of the world — is as destructive as it was baseless,” he said in a statement.

Clapper said, “Certainly the Russians have to be chortling about the success of their efforts to sow dissension in this country.”