The final months of the 2020 presidential campaign will see dozens of former Republican national security officials — including some who worked for Trump — actively campaign for a Democrat to win the presidency. They are part of the growing anti-Trump conservative movement that is fighting for their own party to lose — and hoping for a role in a post-Trump GOP.

Seventy former Republican officials from various national security agencies pledged in an open letter Thursday to vote for the Democratic nominee, former vice president Joe Biden. They will mount a campaign in swing states to advocate for the leader of the party they have opposed their whole lives.

“While we — like all Americans — had hoped that Donald Trump would govern wisely, he has disappointed millions of voters who put their faith in him and has demonstrated that he is dangerously unfit to serve another term,” the letter states. “In contrast, we believe Joe Biden has the character, experience, and temperament to lead this nation. We believe he will restore the dignity of the presidency, bring Americans together, reassert America’s role as a global leader, and inspire our nation to live up to its ideals.”

Several of these former officials have spoken out about Trump before, including former CIA director Michael Hayden, former director of national intelligence John Negroponte, former defense secretary Chuck Hagel, former deputy secretary of state Richard Armitage and Kori Schake, vice president for foreign policy at the American Enterprise Institute, a conservative think tank.

What’s new is these officials have linked up with the larger anti-Trump conservative infrastructure to raise hundreds of thousands of dollars to get their message out, especially in Pennsylvania, Wisconsin, Michigan, Arizona, North Carolina and Florida. They built a machine to take down the leader of their own party — and afterward hope to use it to influence the party’s future.

Their letter will appear Friday as a full-page ad in the Wall Street Journal, kicking off a digital and television media campaign targeting centrist voters. The goal is to show real experts targeting Trump on specific policies, highlighting the damage he has done to the national security agencies tasked with protecting us.

“We believe the country just can’t take four more years of a Trump presidency, so it’s therefore up to us to try to raise the alarm and explain in detail the damage Trump has done to the country,” former State Department legal adviser John B. Bellinger III told me.

The Biden campaign, for now, is welcoming the support of national-security-minded Republicans. The Democratic National Convention featured a video Tuesday celebrating Biden’s friendship with Sen. John McCain (R-Ariz.), narrated by his widow Cindy. The GOP officials’ warning that Trump represents a threat to our democracy echoes the speech given by former president Barack Obama on Wednesday night.

If Biden wins, these GOP officials won’t necessarily support Biden’s agenda and aren’t likely to get jobs in Biden’s administration. For those still aspiring to careers in GOP foreign policy, actively supporting Biden is a huge gamble. Even former national security adviser John Bolton, no friend of Trump’s, hasn’t gone that far.

The GOP letter says that the time to debate policy issues will come later, but the need to stop Trump is urgent. “We are concerned with what might happen in a Biden administration,” said Bellinger. “But that’s another problem for another day.”

Bellinger’s group joined forces with the anti-Trump conservative group Defending Democracy Together, which includes Bill Kristol and former New Jersey governor Christine Todd Whitman, who also spoke at the Democratic convention. The group’s executive director, Sarah Longwell, advises a different anti-Trump group of conservative lawyers called Checks & Balances, which includes Bellinger and George T. Conway III, a Post contributing columnist.

Defending Democracy Together in May started the initiative Republican Voters Against Trump. The group has raised almost $20 million to campaign against Trump, according to Longwell. Last week, they put out an ad where former Trump administration Homeland Security official Miles Taylor called Trump’s national security approach “dangerously chaotic.”

“The goal of all of this is to elevate these voices,” Longwell said. “We want to help tell that story not just to Washington Beltway insiders, but to take that case to the American people.”

All these anti-Trump conservative groups know that if they succeed in helping to vanquish Trump, they will have destroyed their principal reason for existence: to oppose Trump. Some are planning to shift gears and focus on issues such as rule of law or reforming government institutions. Others will try to participate in the coming civil war within the GOP.

If Trump loses, the GOP will have to decide if Trump’s foreign policy was an aberration or what the party now stands for, as they move to the opposition and prepare for 2024.

Read more: