A group of leading GOP national security experts — including former homeland security secretary Tom Ridge — urged congressional Republicans on Monday to demand President Trump concede the election and immediately begin the transition to the incoming Biden administration.

“President Trump’s refusal to permit the presidential transition poses significant risks to our national security, at a time when the U.S. confronts a global pandemic and faces serious threats from global adversaries, terrorist groups, and other forces,” said a statement signed by more than 100 GOP luminaries.

The Post's Ashley Parker explains why some Republicans followed President Trump's lead in denying the reality of the election and the danger they're posing. (The Washington Post)

The signers included Ridge, the former Pennsylvania governor who served as homeland security secretary under President George W. Bush, former CIA director Michael Hayden and John D. Negroponte, who served as director of national intelligence.

The message called on “Republican leaders — especially those in Congress — to publicly demand that President Trump cease his anti-democratic assault on the integrity of the presidential election.”

Trump has refused to acknowledge his defeat to Democrat Joe Biden and continues to wage a clamorous, unsuccessful bid to overturn the election’s outcome in several key states that turned the race in Biden’s favor. In the popular vote, Biden is projected to best Trump by a margin of approximately 6 million.

In a nod to these developments, the statement’s signers urged Republican leaders to “strongly oppose” Trump’s “dangerous and extra-legal efforts to intimidate state election officials and distort the Electoral College process.”

Asked about the former officials’ statement, Senate Majority Leader Mitch McConnell’s office on Monday referred to comments he made last week dismissing requests to speak out. “In all of these presidential elections we go through this process. What we all say about it is frankly irrelevant,” McConnell (R-Ky.) told reporters Tuesday. “All of it will happen right on time, and we will swear in the next administration on January 20.”

A spokesperson for House Minority Leader Kevin McCarthy (R-Calif.) did not respond to a request for comment, nor did the White House.

The national security officials’ statement was released hours before officials in Michigan certified the election results in that state showing Biden defeated Trump by more than 155,000 votes. Last week, the president personally called a county canvas board official in Wayne County, Mich., home to Detroit. That official subsequently tried to rescind her vote to certify results there.

“President Trump’s continued efforts to cast doubt on the validity of the election and to interfere in state electoral processes undermines our democracy and risks long-term damage to our institutions,” the statement says.

The organizers of Monday’s statement also led efforts before the election to get Republican national security experts and others to support Biden over Trump. Among other initiatives, they published a newspaper ad signed by many of the same names that appeared on Monday’s statement. The organizers said they were motivated by concern that so many Republican leaders have declined to repudiate Trump’s unfounded election claims.

“It was a sense of both alarm that the president of the United States is trying to undermine our election . . . and disappointment that so many Republican leaders are abetting that effort either with active support or with their silence,” said Ken Wainstein, a former U.S. attorney for Washington, D.C., who later served during the George W. Bush administration as assistant attorney general for national security.

Another organizer of the effort, John B. Bellinger III, said that he encouraged the statement out of dismay that many congressional Republicans have remained silent. Bellinger served as legal adviser to the National Security Council and the State Department during the George W. Bush era.

“It is shocking to me and other senior national security officials, who have dedicated much of our careers to protecting the country, that congressional Republicans are allowing Trump to impugn the integrity of our elections,” Bellinger said, adding that elections are “the very core of American democracy.”

Negroponte, who served nine successive presidents, said of the Trump team: “They’re in denial about the loss and therefore not allowing the transition to go forward.” It takes time to identify and vet nominees for core jobs within the new government, including the roughly 1,000 or so people who need Senate confirmation, he said. “Every day that’s lost is not only unfair to the new administration, it’s harmful to the country and our national security.”

Blocking the transition, he said, “is wrongheaded. It’s just immature.”

Hayden, who as CIA director briefed then-President-elect Barack Obama in 2008 on covert action programs, said the agency “very much” wants to brief Biden but is being prevented from doing so. “That,” he said, “is very concerning.”

The statement added to complaints from a small but growing number of Republicans who describe Trump’s election response as a threat to the nation’s security.

“The Republican Party is not going to be saved by hiding in a spider hole,” Trump’s former national security adviser, John Bolton, said during an appearance Sunday on CNN’s “State of the Union.” Bolton is not among those who signed the statement. “We need all of our leaders to come out and say, ‘The election is over.’ We’re not talking about an abstract right for Trump to use his legal remedies. We’ve passed that.”