Steve Bannon listens as Trump delivers remarks | Nicholas Kamm/AFP via Getty Images Mega-donor urged Bannon not to resign Trump’s strategist threatened to leave the White House after clashing with Jared Kushner.

The man credited with honing Donald Trump’s populist message and guiding him into the White House has grown frustrated amid continued infighting in the West Wing, so much so that in recent weeks a top donor had to convince him to stay in his position.

Five people, including a senior administration official and several sources close to the president, tell POLITICO that Bannon, one of Trump’s closest advisers, has clashed with the president’s son-in-law Jared Kushner, who’s taken on an increasingly prominent portfolio in the West Wing. Bannon has complained that Kushner and his allies are trying to undermine his populist approach, the sources said.

Republican mega-donor Rebekah Mercer, a longtime Bannon confidante who became a prominent Trump supporter during the campaign, urged Bannon not to resign. “Rebekah Mercer prevailed upon him to stay,” said one person familiar with the situation.

Another person familiar with the situation, a GOP operative who talks to Mercer, said: “Bekah tried to convince him that this is a long-term play.”

Bannon has worked closely with Mercer not only at the right-wing website Breitbart News, where her family is a major investor and where he served as executive chairman until joining the Trump campaign in August, but also at Cambridge Analytica, the data-analytics firm owned largely by the Mercers. Bannon is a part owner of the firm, though he’s trying to sell his stake, and until recently he served as vice president of the company’s board.

The White House said that Bannon had not taken any steps to leave, and Bannon told POLITICO that any suggestion he threatened to resign was “total nonsense.”

At Breitbart, Bannon, 67, was amongst the earliest Trump supporters and is credited with building the ideological foundation of the Trump movement. A former investment banker of considerable means, he is somebody the president views as an equal – and whose departure would scramble the pecking order of a White House that seems to have chaos in its DNA.

“It hasn’t all been fun, and I know he’s been frustrated,” said a Republican who has spoken with Bannon in recent weeks. His position in the West Wing took a blow on Wednesday, when the White House issued a national security directive removing him from the National Security Council, where he had been installed as a member in the first weeks of the administration.

Bannon opposed the change, even saying he’d quit if the president signed off on it, according to one person familiar with the situation.

His allies inside the White House downplayed the significance of the reassignment, casting his initial elevation to the NSC as a temporary position that had come to a natural conclusion.

But Bannon's removal from the NSC is symbolic of a broader realignment in the West Wing that has Bannon increasingly marginalized and at odds both with the president and Kushner.

Bannon has generated a thrum of controversy since he joined the Trump campaign as chief executive in August, and the consistent drumbeat of negative press coverage that has surrounding him has strained his relationship with Trump, who monitors media reports closely, according to a source familiar with the situation.

His removal from the National Security Council was symbolic of a broader realignment in the West Wing. Bannon has generated a thrum of controversy since he joined the Trump campaign as chief executive in August, and the consistent drumbeat of negative press coverage that has surrounding him has strained his relationship with Trump, who monitors media reports closely, according to a person familiar with the situation.

Bannon has also butted heads with Kushner, the president’s son-in-law and senior adviser, who considers him an ideologue whose advice to Trump is making it harder for the president to win popular support for his agenda, according to people familiar with the dynamic.

The tension between the two is indicative of a larger power struggle in the White House as Kushner’s prominence and responsibility have ballooned. He has helped to expand the authority of two senior West Wing officials who, like him, are less ideological in nature: former Goldman Sachs executives Gary Cohn, who is now chairman of the National Economic Council, and Dina Powell, the deputy national security adviser for strategy. The national security directive removing Bannon from the NSC explicitly authorized Powell to attend the National Security Council's Principals' and Deputies' Committee meetings.

The “big fight is between nationalists and the West Wing Democrats,” said a person familiar with Bannon’s thinking.

“You have these New York interlocutors who are just not political and who want to think that they’re above the way Washington thinks, but if anybody is allied on delivering on things that Trump ran on, it’s Bannon and Reince and the vice president,” said the Republican who has spoken to Bannon recently.

Kushner has also told people that he thinks Mercer as well as her father, the hedge fund billionaire Robert Mercer – who poured $13 million into a super PAC that supported Ted Cruz’s campaign in the Republican primary, and came around to Trump after he won the nomination – have taken too much credit for their role in his victory, and has expressed misgivings about their go-it-alone approach to outside spending boosting Trump’s agenda.

“If Bannon leaves the White House, Bekah’s access and influence shrinks dramatically,” said the GOP operative who talks to Mercer.

Alex Isenstadt contributed to this report.