After 24 years in office, Brooklyn District Attorney Charles J. Hynes went down in defeat Tuesday night in New York City’s Democratic primary.

In the end, both those who admired Hynes and those who had come to vilify him can likely now agree on one thing: He had simply stayed in office too long.

It seems inarguable, after all, that the known perils of comfortable incumbency – complacency, arrogance, worse – played some role in Hynes’s defeat. Such accusations had been at the heart of what proved to be the successful campaign of Kenneth P. Thompson, a former federal prosecutor who will now become the first African-American district attorney in Brooklyn’s history.

"The Democratic voters of the county today decided that there should be a change in this office and its direction," Hynes said in a concession speech Tuesday night.

Hynes had come into office in 1990 as a civic champion, a special state prosecutor who had investigated the notoriously corrupt nursing home industry and who had won convictions against members of a white mob who chased a black man to his death in Howard Beach, Queens. He exits with what many regard as a record of innovation, but also with what many had come to see as a record of troubled prosecutions and cronyism and personal vendettas.

The New York Daily News, a reliable backer of Hynes over the decades, endorsed Thompson, asserting that Hynes had presided over an array of “miscarriages of justice.”

Hynes's ouster gives rise to a number of things worth considering:

1. Pure appreciation of how rare such a defeat is. Not since 1955 had an incumbent district attorney been unseated in New York City by way of the ballot box. In Brooklyn, the last time an incumbent prosecutor was removed via the vote came in 1911. That’s not a typo: 1911.

Richard Brown in Queens has been in office since 1991. Robert Johnson in the Bronx has been the borough’s top prosecutor since 1989. Robert Morgenthau served as Manhattan district attorney for nearly 35 years before retiring at age 89.

"There is something unique about the district attorney's office that makes the power of incumbency far more powerful than in any other race," Guy V. Molinari, the legendary Staten Island politician, once told the New York Times. "People somehow feel that changing the person in charge of law enforcement somehow would make life easier for the bad guys, the criminals. When it comes to law enforcement, people don't want to disturb the status quo."

2. What about the idea of term limits? There are states and counties around the country where term limits have been imposed on local prosecutors. But the two referenda that placed term limits on locally elected officials in New York City exempted district attorneys.

“I have really mixed feelings about the question of term limits for prosecutors,” said Daniel Richman, a former federal prosecutor who is now a professor of law at Columbia University. “DAs have a tendency to get entrenched. And I’m not sure that leads to the exercise of the kind of zeal and good judgment that we expect of people with such powers. That said, I’m not sure more politics and more elections is the solution.”

The notion of term limits faces particular challenges in New York, and the saga of the efforts by voters on Long Island to impose term limits on a local prosecutor is instructive.

In 2001, voters in Nassau County appeared to have spoken: No district attorney could serve longer that 12 consecutive years in office. Term limits, the voters made clear in a referendum, ought to be imposed not only on those who enact laws – the county legislators - but on those charged with enforcing them.

Just last month, however, New York state’s highest court ruled that Nassau County voters had no authority to limit the terms for their district attorney. Local district attorneys, whether in Nassau County or Brooklyn, were in certain respects officers of the state, and only the state could determine how long they could remain in office.

There is thus little chance of term limits for district attorneys in New York being adopted anytime soon. Term limits for state officials has gained no traction over the years, and most experts agree the legislators are unlikely to adopt laws limiting their time in office.

“It’s clear to me the best way to address the question of prosecutors being in office too long would be for them to, at some point, agree to step aside,” said Richman, the Columbia professor. “It’s also clear to me that’s never going to happen.”