It’s a tenet of the intelligence business that spies are supposed to avoid the political fray, declaring allegiance to no party or candidate, and speaking the unvarnished truth to whomever is in power.

Donald Trump has turned that tradition on its head. Compelled by a candidate whom they say poses a unique threat to U.S. foreign policy and security, dozens of current and former intelligence professionals have in the past few months lept into the political arena in an unprecedented, coordinated effort to keep a presidential nominee from being elected.

This is new territory for American spies, who, when they do criticize politicians, tend to do it retrospectively in score-settling memoirs or op-eds, and not in the heat of a presidential campaign. But just as the 2016 election has departed from tradition in so many ways, intel professionals are now feeling unleashed to try to block Trump and help his opponent get elected.

Longtime spies and security experts have derided Trump as a Russian stooge; an unrepentant demagogue whose rhetorical attacks on Muslims have alienated the very people the U.S. wants to enlist in an international fight against terrorism; and a neophyte whose whose militant ignorance and hostility to expertise makes him fundamentally unfit to hold the nation’s highest office.

“Many intelligence officials are horrified by a candidate who is not just a foreign policy ignoramus, but who seems so contemptuously uninterested in discussing nuances and complexities. I can’t imagine having to be his intel briefer,” Matthew Waxman, who served in top positions at the Defense Department and the National Security Council during the George W. Bush administration, told The Daily Beast.

Waxman was one of 50 former national security and foreign policy officials , who have all served in Republican administrations, to sign an open letter this week declaring that Trump would “put at risk our country’s national security and well-being.”

That letter was preceded by one in March, signed by 121 GOP national security experts and former officials , who said Trump is a “fundamentally dishonest” person who “would use the authority of his office to act in ways that make America less safe, and which would diminish our standing in the world.”

And last week, in a blistering op-ed in The New York Times, former CIA deputy director Michael Morell endorsed Democratic nominee Hillary Clinton and argued that Trump is “already damaging our national security” by promising to ban Muslims from entering the United States, an idea that “clearly contradicts the foundational values of our nation, [and] plays into the hands of the jihadist narrative that our fight against terrorism is a war between religions.” Morell is presumed to be on a short list for CIA Director in a future Clinton administration, and some read his op-ed both as a condemnation of one candidate, and an attempt to ingratiate himself with another.

On occasion, top intelligence officials have endorsed a presidential candidate. In 1996, for instance, former CIA Director James Woolsey backed Republican Sen. Bob Dole over Woolsey’s former boss, incumbent president Bill Clinton. And intelligence veterans who campaigned for would-be presidents have come back to government to serve them: The current CIA Director, John Brennan, was a retired intelligence officer when he became Sen. Barack Obama’s national security adviser in the 2008 campaign.

But half a dozen former officials and historians told The Daily Beast that they’d never seen so many intelligence professionals come forward in opposition to a candidate as they have with Trump.

“It is the volume this time that is completely new,” said Timothy Naftali, an intelligence historian and professor of national security studies at New York University.

Trump’s critics are especially unnerved by the mutual admiration society he has formed with Russian President Vladimir Putin , himself an ex-spy who joined the KGB in 1975, in his early twenties, and served until the fall of the Soviet Union.

“I believe Trump’s apparent bromance with Putin offends the core of anyone familiar with that former KGBer, which means practically anyone in the U.S. intelligence community past or present,” Naftali said. “When you add to that Trump’s apparent inability to understand that we need the help of Muslims around the world and at home to defeat violent Islamic extremism, the deep concern about a Trump presidency expressed by top intelligence professionals is hardly surprising.”

If the spooks have broken with tradition, they say that it’s because Trump himself has departed so radically from acceptable behavior for a presidential candidate.

“A very broad array of national security and intelligence officials see Trump as outside the zone of reasonable policy disagreement and character fitness,” Waxman said.

Several have said they don’t think the public opposition to Trump from the intelligence community is out of line, despite its unprecedented nature.

“If these people had made these statements while still in office, it would’ve been a terrible precedent,” said Joel Brenner, the former inspector general for the National Security Agency and the former head of U.S. counterintelligence in the George W. Bush administration. “But they’re not in office, and there’s nothing new in having retired officials speak their minds. They’re doing their duty as citizens in the face of a hateful and horrifically dangerous candidate.”

Brenner continued, “The question is why the leaders of the Republican party haven’t said the same thing. They know it’s true.”

Like elected officials, intelligence vets have seen the inner workings of government close enough to form an opinion on how Trump is likely to perform in office.

“A lot of these folks have seen White House decision making up close under several presidents. They know that the entire White House soon comes to reflect the style and temperament of the president, and that there are very few checks there on his discretion in foreign policy and intelligence matters,” said Stewart Baker, a former general counsel at the NSA and the top policy official at the Homeland Security Department during the last Bush administration. “So they’re worried that Trump’s willingness to rethink longstanding security principles on the fly will lead to big and potentially dangerous changes in policies that they lived under throughout their careers.”

Not all ex-intelligence officers have sided against Trump. Retired Gen. Michael Flynn, who ran the Defense Intelligence Agency from 2012 to 2014, is a top national security adviser to the Republican nominee and was a finalist to be his running mate. Flynn has railed against Clinton for her use of a private email server, and at one point demanded that she withdraw from the race until the Justice Department had reached a decision on whether to prosecute her. (Last month, the department declined to do so on the recommendation of the FBI director , James Comey.)

But Flynn is alone among his colleagues in backing Trump. And his withering assaults on Clinton are another sign that the old inhibitions on intelligence officials entering the political ring have fallen away.

In some respect, the road to this hyper-political environment was paved by retired military officers, like Flynn, who’ve taken up the partisan mantle when they step out of uniform. In 2006, half a dozen retired generals blasted Defense Secretary Donald Rumsfeld’s handling of the Iraq War, a public campaign of criticism that some likened to a revolt. And at the Democratic convention in Philadelphia in July, retired Gen. John Allen spoke on behalf of Clinton.

Retired Chairman of the Joint Chiefs Martin Dempsey criticized Allen and Flynn, who spoke at the GOP convention in Cleveland, for politicizing national security affairs. “As generals, they have an obligation to uphold our apolitical traditions,” Dempsey wrote in a letter to The Washington Post . “They have just made the task of their successors—who continue to serve in uniform and are accountable for our security—more complicated.”

Neither Flynn nor Allen will put on the uniform again. But they could return to public service, as could any number of intelligence veterans who are openly parting ways with Trump or backing Clinton.

Baker, the former NSA general counsel, said taking a side now risks the credibility of intelligence professionals in the next administration.

“If [Trump] wins and comes into office thinking that the intelligence community has joined the opposition, it will be bad for the IC and the country,” Baker said. On the other hand, he said, an endorsement of Clinton by a top former official, like ex-CIA official Morell, raises questions about whether professionals can be impartial.

“It’s hard to be comfortable, if Hillary Clinton wins, with someone getting the CIA job by dint of overt partisan campaigning. That’s not the way we want the job to be won, and certainly not how we want the job carried out,” Baker said.

Clearly, the rules have changed. And perhaps former officials have been taking their some of their cues from the top. Privately, intelligence officials and some lawmakers have worried that Trump may leak classified information he receives in a security briefing that’s offered to all presidential nominees.

Brennan, the current CIA director, has said publicly that he wouldn’t carry out orders from any president to torture prisoners, effectively putting him at odds with Trump, who has said he would bring back brutal interrogation techniques such as waterboarding. And while Brennan hasn’t endorsed a candidate, there’s little doubt whose side he’s on.

As Bloomberg’s Eli Lake recently reported, the director is campaigning to continue in his post in a Clinton administration . And in an appearance at the Council on Foreign Relations in Washington in June, Brennan seemed to suggest that he wanted as little to do with candidate Trump as possible .

When PBS journalist Judy Woodruff asked Brennan if would personally give the intelligence briefing that Trump and Clinton are offered, the director grinned slightly and promised to “fulfill my CIA responsibilities to the best of my ability. And if there is a need for me to be personally involved in this, I will—I will try to carry out my responsibilities.”

Brennan paused, then said, “And if there’s not a need, I will not,” prompting laughter from the audience.