WASHINGTON ― The Justice Department has asked the House Intelligence Committee for more time to comply with its request to provide evidence of President Donald Trump’s allegation that his predecessor wiretapped Trump Tower. The deadline for a response was Monday.

“This afternoon, the Department of Justice placed calls to representatives of the Chairman and Ranking Member of the United States House Permanent Select Committee on Intelligence to ask for additional time to review the request in compliance with the governing legal authorities and to determine what if any responsive documents may exist,” Justice Department spokeswoman Sarah Isgur Flores said in a statement Monday evening.

Trump had asked Congress to investigate his claim, which he tweeted about on March 4, that Barack Obama personally ordered surveillance on Trump Tower before the election. Rep. Devin Nunes (R-Calif.), chair of the House Intelligence Committee, said the committee would look into the matter as part of a broader inquiry into Russia’s interference in the 2016 election.

So far, there is no evidence that Trump’s allegation was anything but a conspiracy theory, perhaps picked up from a right-wing website. If there is proof, Trump seems to be the only person to have it.

“He’s the president of the United States. He has information and intelligence that the rest of us do not,” White House counselor Kellyanne Conway said on March 6.

Conway admitted on Monday that she personally didn’t have any evidence that Obama had ordered wiretapping of Trump, although she put forward the theory that it could have happened through “microwaves that turn into cameras.”

The president has been quiet about his explosive allegation since his original tweetstorm. On Monday, he ignored a reporter’s question about whether the Justice Department would comply with the committee’s request.

White House press secretary Sean Spicer on Monday punted responsibility for providing the Justice Department with evidence of Trump’s claims, telling reporters during his briefing that the committee had specifically asked the agency to respond. He added that there’s “no question that there had been an abundance of reports regarding surveillance and other type of activities that occurred during the 2016 election.”

Trump’s tweets, however, specifically said Obama authorized wiretapping on Trump Tower, and there have been no credible reports backing up that claim.

Mark Wilson/Getty Images President Donald Trump has said he believes that Barack Obama wiretapped him before the election. No one else really seems to believe that.

An Obama spokesman has denied that the former president wiretapped Trump. “Neither President Obama nor any White House official ever ordered surveillance on any U.S. citizen,” the spokesman said. “Any suggestion otherwise is simply false.”

FBI Director James Comey reportedly asked the Justice Department to publicly refute Trump’s claim as well, but the agency has so far not released any such statement. James Clapper, the director of national intelligence under Obama, recently said “there was no such wiretap activity mounted against the President-elect at the time, or as a candidate, or against his campaign.”

On Sunday, Sen. John McCain (R-Ariz.) challenged Trump to offer proof of his claims, saying if the president can’t do so, he needs to retract his allegation.

“The president has one of two choices, either retract or provide the information that the American people deserve,” McCain told CNN. “I have no reason to believe that the charge is true, but I also believe that the president of the United States could clear this up in a minute.”

This piece has been updated with Sean Spicer’s comments from the White House briefing and a response from the Justice Department.

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