In February 2022, two months into his tenure, the Manhattan district attorney, Alvin L. Bragg, made a momentous decision: He would not pursue a criminal case against Donald J. Trump.
He was criticized then for seeming to drop his office’s long-running investigation into the former president. He was criticized later that year, when he appeared to have refocused the investigation on a hush-money payment to a porn star who said she’d had sex with him.
And he was criticized once more several months later, in March of last year, when he became the first prosecutor to indict an American president, charging Mr. Trump with 34 counts of falsifying business records. Critics at the time — including some prominent Democrats — said the case was not strong enough to have brought against a former president.
But on Thursday, shortly after 5 p.m., Mr. Bragg won one of the most consequential trials in American history: Mr. Trump was found guilty on all counts. Jurors determined that he had coordinated an unlawful conspiracy to win the White House in 2016 and had falsified records to cover up his scheme.
“I did my job, and we did our job,” Mr. Bragg said at a news conference on Thursday after the verdict, when asked about the criticism he received about his handling of the investigation and then the case. “There are many voices out there, but the only voice that matters is the voice of the jury, and the jury has spoken.”
Throughout his office’s investigation and the trial, Mr. Bragg had declined to speak publicly about the facts of the case or Mr. Trump himself. On Thursday, Mr. Bragg answered only a few questions and refused to respond to Mr. Trump’s sharp criticisms of him and his office.
Throughout the trial, staff members have said, Mr. Bragg has remained remarkably tranquil, showing little sign of the strain that comes with prosecuting a former president. One staff member who spent time with Mr. Bragg during the last several weeks described him as having been eerily calm.
Despite the momentous stakes of the trial, he remained steady on Thursday — though he appeared to be holding back emotion.
The legal battle pitted two opposites against each other: Mr. Bragg, a Harvard-trained prosecutor who often dodges the media spotlight, and Mr. Trump, the reality-television star turned Republican former president who craves and shapes it.
Mr. Bragg, 50, Manhattan’s first Black district attorney, vowed when he ran for office to bring a new approach to criminal justice in the borough. He said he would take the same approach to prosecuting the rich and powerful as he would to anyone else. And so he brought the case against Mr. Trump, charging the former president with the mundane-sounding crime of falsifying business records.
But as is typical of Mr. Bragg — a legal wonk above almost anything else — the case was more complex than it appeared. In New York, charges of falsifying business records are misdemeanors, unless they are used to commit or conceal another crime. And the district attorney determined that the crime could be the violation of a little-known state election measure that forbids anyone from aiding an election by unlawful means.
The criminal case, despite its critics and complexity, achieved his goals. The jurors delivered a guilty verdict on all 34 counts after roughly 10 hours of deliberations.
“While this defendant may be unlike any other in American history,” Mr. Bragg said on Thursday, “we arrived at this trial, and ultimately today at this verdict, in the same manner as every other case that comes through the courtroom doors: by following the facts and the law, and doing so without fear or favor.”
Mr. Bragg grew up on Strivers’ Row in Harlem and graduated from Harvard Law School with a commitment to service, which he displayed first as a federal prosecutor and then as a deputy New York attorney general. At each turn, he impressed his colleagues with his open-minded, careful consideration of the law.
In his campaign for district attorney, Mr. Bragg was somewhat less cautious than had previously been his practice. On the trail, he brought up Mr. Trump’s name often and played up his history of taking him on in the attorney general’s office.
But asked on Thursday about what sentence he would seek for Mr. Trump, Mr. Bragg sidestepped. His office would answer eventually, he said. It would do so in court.