“My job is to speak for the police, and I’ve been criticized for doing that many times,” Mr. Lynch said on a recent afternoon, defending himself against his challengers’ claim that he overplayed his hand against the mayor. “Was I angry this winter? I was. But so were my members. It’s not my role to be popular or liked. It’s my role to be a voice for my members.”

From the moment that Mr. Lynch, 51, took over the P.B.A. in 1999, that voice has been described with a long if limited list of adjectives: coarse, loud, very loud, strident, harsh, abrasive. His impassioned outrage has more or less defined him throughout his long career, and his critics say it has finally become a liability as he moves toward his first contested election in a decade, at what is also an exceptionally fraught time for his members.

Just last week, speaking about the murder of Officer Brian Moore, who died on Monday after being shot while on patrol in Queens, William J. Bratton, the police commissioner, said he had not seen “so much anti-police sentiment” since the early 1970s. Much of the rage has been fomented by the police killings of young black men across the country, leaving Mr. Lynch and his 23,000 members to grapple with the feeling among some people that they are a lawless occupying force.

Both of the men who will oppose him in the election — Brian Fusco, a high-ranking P.B.A. official and 27-year department veteran, and Ronald Wilson, a 28-year veteran — contend that Mr. Lynch’s problems go beyond his antagonistic personality and are rooted in his failure over the years to uphold his members’ interests. In June 2009, they say, Mr. Lynch was unable to prevent Gov. David A. Paterson from slashing pension benefits for newly hired officers. They also claim that Mr. Lynch delayed until this year taking the current contract squabble into binding arbitration so that the matter would come to a head in the midst of the elections.

A Quinnipiac University poll released around the time of the catering-hall insurrection found that nearly 80 percent of New York voters considered Mr. Lynch’s attacks on Mr. de Blasio “too extreme.” The poll, combined with some hostile editorials and comments by his colleagues — one of whom assailed him as “a throwback to Archie Bunker” — helped establish a narrative that Mr. Lynch was a petulant civil servant whose rancorous dispute with the mayor did damage to his members.