Donald Trump had been in office just a few minutes when he boasted that John F. Kelly looked like a military general straight out of a Hollywood movie, but now the president is holding a likely extended casting call for a more loyal chief of staff — one who will immediately have to navigate a thicket of congressional and federal investigations. 

As Trump searches for what will be his third top aide in two years, Republican insiders see no frontrunner or even a clear list of candidates. But what they really cannot determine is who could coexist with a chief executive who rejects his staff’s attempts to manage him and his bombastic, norms-busting approach to the job.

“See my generals, those generals are going to keep us so safe,” Trump said at a Capitol luncheon shortly after being sworn in on Jan. 20, 2017. “These are central casting. If I’m doing the movie, I’d pick you.”

He gestured at his picks for Defense secretary (James Mattis) and Homeland Security secretary (Kelly). The latter so impressed Trump, especially by echoing his immigration rhetoric and implementing his hardline policies, that he brought Kelly into the West Wing in the summer of 2017 to, as White House Press Secretary Sarah Huckabee Sanders put it Tuesday, deliver “a lot of structure to the White House that was needed at the time he came in.”

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Trump announced Saturday afternoon that the retired Marine Corps general would leave his post at the end of the year, calling him a “great guy” even though they often clashed and had reportedly stopped speaking. Sanders, channeling her boss, revealed some of Trump’s frustrations and his thinking about Kelly’s replacement.

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“That being said, I think the president is looking for somebody who believes in what we’re doing,” she said, appearing to criticize Kelly by saying when senior aides disagree with the commander in chief and his agenda, “they need to do that behind closed doors.”

That came a few hours after Trump claimed he is “interviewing a lot of … great people for chief of staff.” The president often contends he and lawmakers or other world leaders “get along very well.” But Republican sources say it is difficult to imagine any potential chief of staff who could do that for more than a few months.

Fake News has it purposely wrong. Many, over ten, are vying for and wanting the White House Chief of Staff position. Why wouldn’t someone want one of the truly great and meaningful jobs in Washington. Please report news correctly. Thank you!

— Donald J. Trump (@realDonaldTrump) December 11, 2018

GOP strategist Evan Siegfried said the next White House chief of staff “will only be successful if Trump does not undercut and neuter them like he does with all his staff. If Trump is unwilling to be reined in, he will hurt himself and presidency.”

So far, the president has resisted efforts by Kelly and Reince Priebus, his first chief of staff, to do that.

“They’re having trouble filling a position that is generally one of the most desirable in Washington because the president is seen as fundamentally unmanageable,” said Michael Steel, a former adviser to Speaker John A. Boehner and Jeb Bush during his 2016 presidential bid.

Among the names being bandied about to take Kelly’s spot is Office of Management and Budget Director Mick Mulvaney, a former Republican congressman from South Carolina. Treasury Secretary Steve Mnuchin has also been floated.

“Honestly, I haven’t heard any options better than Kelly,” said one Republican source granted anonymity to speak candidly. But the same source called Mulvaney “probably the best option that I’ve heard floated.”

“I don’t get the impression that Mnuchin has strong political antenna,” the source said. 

But Siegfried said David Bossie, Trump’s 2016 deputy campaign manager, would be a “strong” candidate.

“Trump needs to look at the landscape over the next two years and pick somebody who will help him navigate it,” he said, referring to investigations by special counsel Robert S. Mueller III, federal prosecutors in New York, and House Democrats when they take control in January. 

“The president needs to have a proven trench warfare specialist who can navigate Congress,” he said, “both the oversight and legislative aspects — as well as the multiple ongoing investigations into Trump, his campaign and business.”

Further complicating Trump’s search is a new cloud now hanging over the West Wing: the sentencing of Michael Cohen, his former “fixer” and personal attorney.

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After all, on one of the counts that put Cohen in prison for three years, Cohen contends he was merely following his former client’s direction by making payments to an adult film star and a Playboy model to keep their allegations of extramarital affairs with Trump under wraps in the run-up to the 2016 election. Cohen told federal prosecutors he did so fearing the women might go public and hamstring or end Trump’s White House hopes.

In an emotional statement in a New York courtroom Wednesday, Cohen blamed his actions on a “blind loyalty” to the president that he said “led me to choose a path of darkness over light.” Cohen added: “Time and time again, I felt it was my duty to cover up his dirty deeds.”

While cleaning up a president’s “dirty deeds” is not exactly in the chief of staff’s job description, the person Trump chooses to replace the soon-to-depart John Kelly will have to be loyal to the president and follow his orders.

House Democrats are preparing to tear into Trump’s business and 2016 campaign, including things done by a man who was, in some ways, his private-sector chief of staff. But Republican members continue standing by their president.

“It doesn’t do me any good to comment on whether the president should be worried or not, so I’m not going to do that,” Georgia Republican Sen. Johnny Isakson said Wednesday. “We should all be worried that we’re not focusing on the main thing we have got to do, and that is getting this country heading in the right direction.”

Kellie Mejdrich contributed to this report.