The Donald Trump transition, already off to slow start, bogged down further Tuesday with the abrupt resignation of former Congressman Mike Rogers, who had been coordinating its national security efforts.

Two sources close to Rogers said he had been the victim of what one called a “Stalinesque purge,” from the transition of people close to New Jersey Gov. Chris Christie, who left Friday. It was unclear which other aides close to Christie had also been forced out.

The Trump transition did not immediately respond to a request for comment.

Rogers confirmed his exit in a statement that said that, despite his departure, he planned to continue to "provide advice and counsel as needed to the incoming Trump administration."

He and his top aide had been working for months, preparing the groundwork for transition. Two sources close to the situation described an atmosphere of sniping and backbiting as Trump loyalists position themselves for key jobs.

“It was a privilege to prepare and advise the policy, personnel and agency action teams on all aspects of the national security portfolio during the initial pre-election planning phase. Our work will provide a strong foundation for the new transition team leadership as they move into the post-election phase, which naturally is incorporating the campaign team in New York who drove President-elect Trump to an incredible victory last Tuesday,” Rogers said in the statement.

Congressman Rep. Mike Rogers (R-MI). Chip Somodevilla / Getty Images, file

Rogers was initially seen as a leading candidate for CIA director, but now is likely off the list, a source told NBC News. Rep. Devin Nunes, the Republican chairman of the House Intelligence Committee, is now a top contender.

Rogers' departure follows Christie’s demotion from head of the team to a vice-chair, with Vice President-elect Mike Pence taking over for him last week.

The purge indicates the emphasis on loyalty — and significant influence of Trump son-in-law Jared Kushner, husband of Ivanka — that characterized Trump’s campaign will carry over into his White House.

Multiple sources indicated that Christie was demoted because he wasn’t seen as sufficiently loyal to Trump, failing to vocally defend him at key moments on the campaign trail.

But he has long been in a precarious position with Trump, due in part, multiple sources say, to a longstanding grudge sparked when Christie prosecuted Kushner's father in 2004. Due to Christie’s investigation, Charles Kushner eventually pleaded guilty to 18 felony counts, including tax fraud and witness tampering, and was sentenced to two years in federal prison.

Rogers’ exit and Christie’s demotion are the latest wrinkles in a transition process that’s gotten off to a rocky start following Trump’s unexpected election victory last week.

The Trump transition has yet to take up offices in the State Department or the Pentagon, government officials tell NBC News, and as of last night Trump had not received an intelligence briefing.

The vice president-elect, Mike Pence took over the transition Friday after Christie’s sudden resignation.

But since Christie had signed the legal paperwork, not Pence, the transition hit a bureaucratic snag, a transition aide said.

Trump over the weekend named RNC Chair Reince Priebus his chief of staff and Breitbart Founder Steve Bannon chief strategist, earning plaudits with the first but backlash over the former, because of Bannon’s controversial comments on minorities and Breitbart’s often incendiary reporting, among other issues.

In a separate development, Eliot Cohen, a senior State Department official under George W. Bush who blasted Trump during the campaign, ripped into the president-elect's transition effort Tuesday.

After exchange w Trump transition team, changed my recommendation: stay away. They're angry, arrogant, screaming "you LOST!" Will be ugly. — Eliot A Cohen (@EliotACohen) November 15, 2016

Cohen, one of 122 Republican national security figures who signed an open letter last spring opposing Trump's candidacy, had written an essay last week in which he suggested that military and intelligence officials "continue to do their jobs."

But on Tuesday, he tweeted, “After exchange w Trump transition team, changed my recommendation: stay away. They're angry, arrogant, screaming 'you LOST!' Will be ugly.”