President-elect Donald Trump. Zach Gibson/Getty Images President-elect Donald Trump has alienated many of the nation's most senior national security officials and veteran foreign policy experts, leaving him with an apparent shortage of qualified Republicans willing to serve in his administration.

Trump's transition team — many of whom are relative political outsiders who apparently didn't realize that President Barack Obama's entire West Wing staff would have to be replaced — are reportedly scrambling to fill the transition team and make other political appointments before Inauguration Day.

Reuters noted that Trump "will eventually need to fill roughly 4,000 open positions."

A sampling of the troubles: Mike Rogers, a former FBI agent and Michigan representative who chaired the House Intelligence Committee, was leading Trump's national security transition team before he abruptly left, Bloomberg reported. He was one of the few political insiders on Trump's team.

Some staff members on the National Security Council, meanwhile, are thinking of quitting before Trump even enters the White House, The Daily Beast reported last week.

And at least 100 GOP national security leaders — most of whom served in previous Republican administrations and would be among the most highly qualified Republicans to advise Trump on foreign policy — effectively ruled themselves out after signing open letters in March and August saying he was "hateful," "dishonest," "dangerous," "erratic," and generally unfit for the presidency.

Trump has consistently brushed off criticism from establishment figures. He dismissed the August letter as the "failed Washington elite looking to hold onto their power," thanking them for "coming forward so everyone in the country knows who deserves the blame for making the world such a dangerous place."

Donald Trump and Steve Bannon with a park ranger in Pennsylvania. AP Photo/ Evan Vucci

But the letters were a preview of the animosity between Trump and veteran policy advisers that has made it difficult for him to find qualified personnel — especially given his notoriously vengeful nature.

Eric Edelman, a former US ambassador to Turkey who signed the August letter, told Business Insider on Monday that he was never willing to serve in a Trump administration.

But he said he wouldn't be surprised if "people like me" were blacklisted by Trump and his aides for speaking out against him during his campaign.

"They just won an unexpected victory. They were reviled by people like me, and now they are exulting in their success," said Edelman, who has served in senior positions at the State Department, Defense Department, and White House. "That is politics and, as the saying goes, it ain't beanbag."

Paul Rosenzweig, a former senior official at the Department of Homeland Security under George W. Bush, put it even more bluntly in an interview with The Daily Beast.

"Everybody who has signed a Never Trump letter or indicated an anti-Trump attitude is not going to get a job," he said. "And that's most of the Republican foreign policy, national security, intelligence, homeland security, and Department of Justice experience."

President Barack Obama meets with President-elect Donald Trump in the Oval Office. Thomson Reuters

Peter Feaver, who served on the National Security Council under presidents Bill Clinton and George W. Bush, said that when he and his peers signed the letter in August they understood they were moving their names from the "available to be considered" list to the "very unlikely to be considered" list.

"While every administration reaches beyond its narrow base of hardcore supporters to build out its staff, it would be very rare for an administration to hire people who actively spoke out against the president-elect during the campaign," Feaver, who now teaches political science and public policy at Duke University, told Business Insider.

"Fortunately, there are many very capable people who did not sign or speak out and so should not be on any blacklist," he added.

According to The Daily Beast, however, many of the people being vetted by Trump's transition team with respect to national security have field experience from serving in the military but have never navigated the politics of Washington's intelligence community.

"From names I see in the press, the one and only person being vetted that I consider a very experienced hand in foreign and security affairs is Stephen Hadley," Jaap de Hoop Scheffer, NATO's Secretary General from 2005-2009, said during a press call on Tuesday.

Hadley, who served as George W. Bush's National Security Advisor and is now on the board of the US Institute of Peace, has been floated as Trump's possible secretary of defense pick.

Rudy Giuliani and Donald Trump. Mike Segar/Reuters Former New York City Mayor Rudy Giuliani and former US Ambassador to the United Nations John Bolton, meanwhile, are among Trump's top picks for secretary of state. Bolton — generally more of a foreign policy hawk than Trump, based on the views Trump espoused on the campaign trail — served for less than two years and has long been highly critical of the UN.

Giuliani, who was mayor during the September 11, 2001, terror attacks, joined the Iraq Study Group when it was formed in 2006 as a bipartisan assessment of the situation there. But he missed all of the meetings and was later replaced. He has also said he is "not sure" that waterboarding is torture, even though the practice has been banned under US law.

"It depends on how it's done," the former mayor said at a town hall meeting in 2007, when he was running for president. "It depends on the circumstances. It depends on who does it."

Minutes later, he said that "America should not allow torture" but "should engage in aggressive questioning of Islamic terrorists."

The Republican national security officials who denounced Trump in their letters mentioned his generally favorable stance on torture as a major reason they could not support his candidacy. Stephen Biddle, an adjunct senior fellow for defense policy at the Council on Foreign Relations, told Business Insider last week that there would likely be "serious civil-military tensions over issues like torture that raise legal and ethical questions" in a Trump administration.

Many national security veterans are prepared — and even proud — to not be associated with a Trump White House.

Eliot Cohen, a former State Department officer and Defense Department official who signed the August letter, also said it would not surprise him "in the slightest" if Trump had effectively blacklisted those in the national security community who had spoken out against him.

"If its true, I'll wear it as a badge of honor, though," Cohen told Business Insider on Monday. "And you can quote me on that."

Cohen wrote last week that rather than move to Canada, Americans dismayed by a Trump administration should maintain "constant vigilance" over the US's free institutions and "say yes" if they're asked to work for him.

But by Tuesday morning, he'd changed his mind.

"After exchange [with] Trump transition team, changed my recommendation: Stay away," Cohen tweeted. "They're angry, arrogant, screaming 'you LOST!' Will be ugly."

The Trump transition team didn't respond to a request for comment on this story.