New York’s largest public sector union won’t endorse a presidential candidate this year — in a blow to Kamala Harris from a group that has backed Democrats at the top of the ticket for at least 12 years.

The Civil Service Employees Association quietely decided against endorsing in the presidential race after internal backlash to the influential union’s leadership pick of Democrat Joe Biden in 2020.

“In some cases, CSEA determined the best opinion was a no endorsement and to stay out of that particular race,” a part of the webpage on the union’s website full of down ballot endorsements reads.

A spokesperson subsequently confirmed that CSEA was not endorsing in the presidential race this year, but did not reply when asked for further comment. The CSEA had backed Democrats for president for at least three election cycles, though it has often backed Republicans in other races.

The union’s pick of Biden four years sparked a public stir with some members railing that the endorsement didn’t reflect the will of rank-and-file voters.

“Joe Biden clearly aligns with the majority of issues that concern our union and impact working men and women in public service, and weʼre going to do everything in our considerable power to get him elected,” CSEA President Mary Sullivan wrote in a 2020 Facebook Post announcing the union’s endorsement of Biden.

The comment section of the post quickly devolved into a sounding board for disgruntled members who supported Republican Donald Trump.

“Why don’t members get a say in who our union endorses? I don’t endorse Biden. He never did anything for US workers during his entire time in office,” one purported union member wrote in the comments.

“Wow, just like you supported [then-Gov. Andrew] Cuomo for his re-election. Not proud to be a union member, maybe I should stop paying the union dues since you’re not supporting us,” another wrote.

The union’s Facebook post and tweet with the endorsement were later deleted.

The union had endorsed Secretary of State Hillary Clinton in 2016.

CSEA has approximately 200,000 members largely comprised of municipal workers. As of 2010, the union had around 300,000 members.

“CSEA has lost about 10 percent of its membership over the past 5 years. A portion of that was from people choosing not to pay dues, and that’s understandable when you look at how much of the money is supporting political activity in DC,” Ken Girardin, director of research at the Empire Center, opined to The Post.

CSEA is an affiliate of American Federation of State, County and Municipal Employees, AFSCME and the AFL-CIO.

The executive board of the Public Employees Federation, another large public sector union, endorsed Vice President Kamala Harris earlier this year.