Mr. Manafort soon had plenty of detractors among the campaign staff. He won few points by calling Mr. Trump “Donald” in his first CNN appearance, as if he were Mr. Trump’s peer. Some aides suggested he was unfamiliar with all the changes in politics — most notably the rise of the internet — since 1996, when he last worked on an American presidential campaign. Others described him as lazy, carefully noting when he took off on Fridays for the Hamptons. Mr. Manafort said he had built a television studio at his home there so he could appear on Sunday talk shows remotely.

He lasted only five months, three of them as campaign chairman. When The New York Times revealed that a ledger found by Ukrainian investigators had listed $12.7 million in off-the-books cash payments to Mr. Manafort’s firm, one former campaign aide said that Mr. Trump was enraged. But another article detailing how Mr. Manafort and others were begging Mr. Trump to stop picking public fights equally angered Mr. Trump. When Jared Kushner, the president’s son-in-law, told Mr. Manafort he was out, Mr. Trump was barely speaking to him.

By then, Mr. Manafort’s financial house of cards was on the verge of collapse. Less than two weeks after he left the campaign, one lender informed him that it had started to foreclose on his Brooklyn brownstone. He had paid cash for it when he was financially flush four years earlier, then borrowed $5.3 million against it that February. Five months had passed with no payments.

Mr. Gates managed to retain his affiliation to Mr. Trump as a liaison between the campaign and the Republican National Committee, although Mr. Trump disliked him so much that he was barred from flying on the candidate’s private plane. Mr. Manafort tried to use his lingering connection to Mr. Trump to land consulting work and to persuade banks to bail him out. He dangled a possible cabinet secretary post in front of Stephen Calk, chairman of Federal Savings Bank in Chicago, pressing Mr. Gates to promote him as a possible secretary of the Army.

He continued to treat Mr. Gates as his aide, asking him how to convert profit-and-loss statements from PDF format into Word in order, prosecutors said, to inflate his income and appear more creditworthy to banks. After the election, Mr. Calk approved two loans to Mr. Manafort for a total of $16 million. Mr. Manafort used some of it to save his Brooklyn property from foreclosure.

But even Mr. Calk was getting worried. On Dec. 7, 2016, he wrote to another top bank official: “Nervousness is setting in.” Less than a year later, Mr. Mueller’s team filed the first of a series of indictments against Mr. Manafort. Mr. Mueller granted a plea deal to Mr. Gates and immunity from prosecution to five of the nearly dozen witnesses for the prosecution.

On Sunday, Mr. Manafort celebrated his 40th wedding anniversary in jail. He was allowed three visits limited to 30 minutes each. A notice on the website for his legal defense fund read: “Paul and his family are reaching out to anyone who can assist him at this time.”