Daniel Penny broke into a smile at midmorning Monday, hugging both of his lawyers in a Manhattan courtroom and getting a kiss on the cheek from one. Moments before, a jury forewoman had said Mr. Penny was not guilty of criminally negligent homicide in the death of a homeless subway passenger he had restrained in a chokehold last year.

As the celebration moved to a nearby bar, criticism of the district attorney, Alvin Bragg, exploded online. It came from Republicans like Vice President-elect JD Vance, Donald Trump Jr. and former Mayor Rudolph W. Giuliani, who praised the jurors and scorned Mr. Bragg for charging Mr. Penny, a former Marine.

On Friday, Mr. Vance said he had invited Mr. Penny to attend the Army-Navy football game on Saturday with him and called Mr. Bragg “New York’s mob district attorney.”

And so, as Mr. Penny’s star ascends on the right, Mr. Bragg, who faces re-election next year, finds himself in a familiar position: saying he had followed the law and his duty no matter the outcome as an internet storm raged around him.

Mr. Bragg, a Harlem native who is Manhattan’s first Black district attorney, has been a target for such fury since the first days of his term, when he promised a progressive approach to crime. It built to a fever when he charged President-elect Donald J. Trump with 34 felonies — and won a conviction on each charge.

After the Penny trial, Mr. Bragg said in a statement that “as with every case, we followed the facts and the evidence from beginning to end.” But he added that “prosecutors and their family members were besieged with hate and threats — on social media, by phone and over email.”