The storm around House Intelligence Committee Chairman Devin Nunes (R-Calif.) intensified Monday after it was revealed that he secretly visited the White House grounds the day before announcing incidental surveillance of President Trump’s transition team.

Nunes struggled to provide an explanation for the unusual trip on Monday even as Democrats demanded that he step aside as leader of the investigation into Russia’s meddling in the U.S. presidential election.

The visit raised questions about whether the White House itself was the source of the mysterious intelligence that Nunes, but no one else on Capitol Hill, has seen. Nunes has vowed to protect his source while offering contradictory descriptions of what the documents reveal.

ADVERTISEMENT

The White House provided little clarity, directing all inquiries to the chairman himself. Since the Trump White House does not make visitor logs public, it remains unclear whom Nunes met with or who let him into the secure facility in the Eisenhower Executive Office Building.

On Capitol Hill, Senate Minority Leader Charles Schumer Chuck SchumerPelosi orders Capitol flags at half-staff to honor Ginsburg Ginsburg in statement before her death said she wished not to be replaced until next president is sworn in Democrats call for NRA Foundation to be prohibited from receiving donations from federal employees MORE (D-N.Y.) called for Speaker Paul Ryan Paul Davis RyanKenosha will be a good bellwether in 2020 At indoor rally, Pence says election runs through Wisconsin Juan Williams: Breaking down the debates MORE (R-Wis.) to remove Nunes as chairman of the Intelligence Committee, while the top Democrat on the Senate Intelligence Committee called the trip “more than suspicious.” The committee’s ranking member, Rep. Adam Schiff Adam Bennett SchiffTop Democrats call for DOJ watchdog to probe Barr over possible 2020 election influence Overnight Defense: Top admiral says 'no condition' where US should conduct nuclear test 'at this time' | Intelligence chief says Congress will get some in-person election security briefings Overnight Defense: House to vote on military justice bill spurred by Vanessa Guillén death | Biden courts veterans after Trump's military controversies MORE (D-Calif.), called for Nunes to recuse himself from the panel’s Russia investigation.

On Tuesday, Nunes reportedly climbed into an Uber, leaving staff members behind, and went to the White House grounds to view classified information brought to his attention by a source.

The next morning, without looping in the top Democrat on his committee, Nunes stepped up to microphones and said he had seen classified information that exposed widely disseminated intelligence collected incidentally — and legally — on Trump transition team members. Nunes served as a member of the Trump transition team’s executive committee.

The chairman briefed Ryan on his findings that morning, but committee Democrats — and many Republicans — were left in the dark.

Then, that afternoon, Nunes returned to the White House to brief Trump on what he had learned.

The strange sequence of events has roiled the Intelligence Committee’s investigation into Russian interference in the election. Nunes has claimed that his findings had no relevance to the Russia probe, yet the committee is examining the unmasking and leaking of surveillance information as part of that investigation.

ADVERTISEMENT

Nunes on Monday denied that there was anything untoward in his Tuesday visit to the White House, pushing back on reports that the venture took place at night and calling the visit “pretty common.”

“At least once a week, if not more than that, we have to go to the executive branch in order to read classified intelligence,” he told CNN’s Wolf Blitzer.

“The sun was out,” he said. “If I really wanted to I could have snuck onto the grounds late at night, but I wasn’t trying to hide.”

Nunes said he was “quite certain that no one in the West Wing knew I was there.”

But Democrats have accused Nunes of acting as an agent of the White House and say he can no longer lead a credible investigation.

“Chairman Nunes is falling down on the job and seems to be more interested in protecting the president than in seeking the truth,” Schumer said on the Senate floor Monday. “If Speaker Ryan wants the House to have a credible investigation, he needs to replace Chairman Nunes.”

Republicans were largely silent on the subject Monday. The Senate Intelligence Committee, which is also investigating Russian election interference, has kept its distance from the controversy.

Nunes did get some cover from a former chair of the committee, former Rep. Pete Hoekstra (R-Mich.), who held the gavel from 2004 to 2007.

“The only important issues are: what was in the materials, are they credible and not fakes. If you get affirmative answers that they are real it doesn’t matter who supplied them,” Hoekstra told The Hill in an email on Monday.

Nunes, meanwhile, said he went to the White House “to confirm what I already knew” about the alleged surveillance.

In an interview with Bloomberg columnist Eli Lake, Nunes said he had heard for over a month about intelligence reports that included details on the Trump transition team, but was only able to view them himself last Tuesday evening.

Nunes told Lake that the source was an intelligence official, not a White House staff member — although press secretary Sean Spicer and Nunes have refused to categorically deny that the White House itself was the source.

Fanning the suspicions further, Trump in a recent interview on Fox News said that he would be “submitting things before the committee very soon,” without providing further details.

Critics have speculated that Nunes’s actions were an attempt to justify Trump’s claim that former President Obama wiretapped Trump Tower during the campaign.

ADVERTISEMENT

Nunes has said repeatedly that the intelligence he viewed did not substantiate that claim.

According to a spokesperson for Nunes, the chairman met with his source at the White House grounds in order to “have proximity to a secure location where he could view the information” — but that explanation did not satisfy intelligence experts.

The House Intelligence Committee makes frequent use of a secure facility in the Capitol — the Sensitive Compartmented Information Facility. His use of the National Security Council office of the Eisenhower building — which, outside of the White House Situation Room, is the main area in the complex to view classified information — is deeply unusual, experts say.

A spokesperson for Nunes said that “because of classification rules, the source could not simply put the documents in a backpack and walk them over to the House Intelligence Committee space.

“The White House grounds was the best location to safeguard the proper chain of custody and classification of these [executive branch documents], so the Chairman could view them in a legal way.”

But that explanation strains credulity, multiple intelligence and classified information experts told The Hill.

“It’s not remotely credible,” said Patrick Eddington, a policy analyst at the libertarian Cato Institute who formerly worked for ex-Rep. Rush Holt (D-N.J.) and at the CIA as an analyst. “The source had to transmit them to the White House in some fashion. Did they take it in a backpack to the White House? Because that would be no different.”

ADVERTISEMENT

“He’s really digging himself in deep,” Eddington said.

Nunes told Lake that he met the source at the White House because it was the most convenient secure location connected to the closed computer system that included the reports, which are only distributed within the executive branch.

“We don’t have networked access to these kinds of reports in Congress,” he said.

Generally speaking, the executive branch can share classified information with the committee electronically, although there are multiple different systems used within government. It is possible that the House Intelligence Committee does not have access to the system in question.

Jordan Fabian and Jonathan Easley contributed.