The New York County District Attorney’s office was the last bastion of the Old Guard of the City. Between Frank Hogan and Robert Morgenthau, they owned the office for 65 years. They were icons. And when Morgy was finally ready to get out of this chair, he passed it to the son of Cyrus Vance, someone he would invite for dinner.

It all changed when Vance, reading the room, decided that it was time to walk away and put the office at 1 Hogan Place, ironically the only address on Hogan Place, into the hands of another, and unlike his iconic predecessor, he had no one to anoint for the position, mostly because it was no longer his to pass over to the next generation of the Old Guard.

But while Cy Vance, Jr. shared the normal New Yorker’s disgust of Trump, on top of the Old Guard disdain for the vulgarity of new money, he left without indicting Donald Trump, kicking the can to his successor, Alvin Bragg. It was now Bragg’s call to make, prosecute Trump or not.

But by the end of the year, the prosecutors had switched gears, in part because Mr. Trump’s lenders had not lost money on the loans but had in fact profited from them. The new strategy was to charge Mr. Trump with conspiracy and falsifying business records — specifically his financial statements — a simpler case that essentially amounted to painting Mr. Trump as a liar rather than a thief.

The two former prosecutors, brought back to lead this historic effort to take down a former president, were big league players, Mark F. Pomerantz and Carey R. Dunne. And they were dedicated to the cause, because as Dunne put it, they wanted to be “on the right side of history.” Not that they were aiming high, as Falsifying Business Records in the First Degree, NY PL § 170.10, is only an “E” felony, and Conspiracy in the Fifth Degree, NY PL § 105.05, only added an “A” Misdemeanor to the mix. Hardly big league crimes. No big time sentences. But it would be a conviction of a former president, a conviction of Trump, and that was big enough.

But an element of the offense was that Trump intended to defraud. Michael Cohen said he did, but there may be no witness less credible and more exposed to being eviscerated on cross than Cohen. Bragg decided he wasn’t going to bet his office on Michael Cohen’s credibility. A wise decision. But if not Cohen, then what?

Mr. Bragg’s choice not to pursue charges is reminiscent of the high hurdle that others have failed to clear over the years as they sought to hold Mr. Trump criminally liable for his practices as a real estate mogul. Mr. Trump famously shuns email, and he has cultivated deep loyalty among employees who might otherwise testify against him, a one-two punch that has stymied other prosecutors in search of conclusive proof of his guilt.

In the Manhattan investigation, the absence of damning emails or an insider willing to testify would make it harder to prove that any exaggerations were criminal. Mr. Trump, who has a history of making false statements, has in the past referred to boastful claims about his assets as “truthful hyperbole.”

It’s easy to presume Trump, for whom neither facts nor truth play an influential role in his conduct, must have committed crimes. But for prosecutors, crimes consist of elements of offenses and evidence to prove their commission. Much of the time, they get away easy, as defendants lack the wherewithal to either conceal their wrongs or mount the fight necessary to prevail against the might of the government. Trump was not going to be so easy to take down, as evidenced by the fight he put up to keep his tax returns secret.

Nor was this the only problem weighing on Bragg’s mind as he began his tenure.

As he was weighing the fate of the Trump investigation, Mr. Bragg was also contending with a firestorm over a number of criminal justice reforms he introduced in a memo his first week in office. The memo immediately embroiled his administration in controversy, a public relations debacle that worsened with a handful of high-profile shootings, including the killing of two police officers in late January.

That’s a lot of controversy for a brand new district attorney, who likely suspected he would be hailed as a hero for his progressive approach, only to learn that the same city that elected Eric Adams mayor didn’t really want a district attorney who misunderstod what the job was.

Already battered, Bragg had to make a critical decision. What was the trade-off between prosecuting Trump and winning and prosecuting Trump and losing. If he won, would he be the hero of the republic? And what if he lost?

The case still was not a slam dunk, Mr. Dunne acknowledged at the meeting. But he argued that it was better to lose than to not try at all.

“It’s a righteous case that ought to be brought,” Mr. Dunne told Mr. Bragg.

Dunne was ready to try and, if it happened, lose. It’s unclear what he meant when he called it a “righteous case,” which usually means one where the prosecutor feels that the defendant is certainly guilty, even if the evidence might not be very strong. To the prosecutorial mind, the connection between certainty of guilt and evidence to prove guilt doesn’t necessarily exist. If they believe he’s guilty, that’s what matters.

But Bragg was a prosecutor. He was an SDNY assistant, a former top AG deputy, and understood what Dunne meant when he called it a righteous case. And it’s not a stretch to presume that Bragg had no feelings of warmth toward Trump, and would have been very happy to be the district attorney who finally convicted him.

On the morning of Feb. 22, Mr. Bragg notified them of his decision: He did not want to continue the grand jury presentation.

Mr. Pomerantz resigned the next day. Mr. Bragg asked Mr. Dunne to stay, but within hours, he joined Mr. Pomerantz in leaving.

While Dunne was ready to die on the hill of Trump’s failed prosecution, Bragg was not. “When you strike at a king, you must kill him,” Ralph Waldo Emerson noted. It’s questionable whether convicting Trump would be accepted by a substantial portion of the nation as anything but a political “witch hunt,” particularly when the offense was relatively petty to begin with. That, of course, couldn’t be helped, as no one is above the law even if a great many people indulge in worshiping a scoundrel.

But the worst thing that could happen to Alvin Bragg was to strike and miss. He was not going to let that happen, no matter how badly some desired to see Trump taken down and how passionately they were certain that he was a criminal.