NEW YORK - Former Defense Secretary Mark Esper has called him a “threat to democracy.” Former national security adviser John Bolton has declared him “unfit to be president.” And former Vice President Mike Pence has declined to endorse him, citing “profound differences.”

As Donald Trump seeks the presidency for a third time, he is being vigorously opposed by a vocal contingent of former officials who are stridently warning against his return to power and offering dire predictions for the country and the rule of law if his campaign succeeds.

It’s a striking chorus of detractors, one without precedent in the modern era, coming from those who witnessed firsthand his conduct in office and the turmoil that followed.

Sarah Matthews, a former Trump aide who testified before the House Jan. 6 committee and is among those warning about the threat he poses, said it’s “mind-boggling” how many members of his senior staff have denounced him.

“These are folks who saw him up close and personal and saw his leadership style,” Matthews said.

“The American people should listen to what these folks are saying, because it should be alarming that the people that Trump hired to work for him a first term are saying that he’s unfit to serve for a second term.”

Yet the critics remain a distinct minority. Republican lawmakers and officials across the party have endorsed Trump’s bid - some begrudgingly, others with fervor and enthusiasm. Many aides and Cabinet officials who served under Trump are onboard for another term, something Trump’s campaign is quick to highlight.

“The majority of the people who served in President Trump’s cabinet and in his administration, like the majority of Americans, have overwhelmingly endorsed his candidacy to beat Crooked Joe Biden and take back the White House,” said Trump campaign spokesman Steven Cheung.

Still, the Biden campaign has trumpeted the criticism of former Trump officials in statements and social media posts, hoping to convince at least some Republican voters - including those who backed other candidates during the GOP primary - that they cannot support his candidacy.

“Those who worked with Donald Trump at the most senior levels of his administration believe he is too dangerous, too selfish and too extreme to ever lead our country again - we agree,” said Biden campaign spokesman Ammar Moussa.

In many ways, the schism among former Trump officials is an extension of his time in the White House. Friction was constant as Trump’s demands ran into resistance from some officials and aides who refused requests that they found misguided, unrealistic and, at times, flatly illegal. Firings were frequent. Many quit.

Staff upheaval was particularly intense in the chaotic weeks after the 2020 election as Trump worked to overturn his election loss to Biden. Trump summoned supporters to Washington on Jan. 6, 2021, as his falsehoods about a stolen election became the rallying cry for supporters who violently breached the U.S. Capitol. Many people serving in the administration quit in protest, including Matthews.

Trump’s attempt to remain in office included a bitter pressure campaign against Pence, who as vice president was tasked with presiding over the count of the Electoral College ballots on Jan. 6. Trump was adamant that Pence should prevent Biden from becoming president, something he had no power to do. Pence had to flee the Senate chamber on Jan. 6 as rioters stormed the building to chants of “Hang Mike Pence!”

Pence recently said he “cannot in good conscience” endorse Trump because of Jan. 6 and other issues, despite being proud of what they achieved.