When a former Democratic congressman running for his old House seat broke ranks last month and endorsed the primary opponent of Representative Jamaal Bowman in a neighboring district, his longtime allies in the left-leaning Working Families Party were furious.
They declared that the former congressman, Mondaire Jones, had “strayed from the values and principles that made us proud to support him,” and canceled plans to actively campaign for his New York comeback bid this fall.
Then things took an even more bizarre turn.
The Working Families Party held what should have been a drama-free primary, but instead of nominating the liberal Mr. Jones, a final tally this week showed that voters overwhelmingly chose the unlikeliest of alternatives as their nominee: a bankrupt local businessman propped up by Republicans.
The story behind the embarrassing upset could hardly be better scripted for a turbulent era in New York politics, complete with Democratic infighting, a starring role by the state’s fast-growing Orthodox Jewish community and Republican meddling that are still coming into view.
But the potential consequences are farther reaching. Mr. Jones’s race against Representative Mike Lawler, a Republican in the Hudson Valley, is a must-win for Democrats trying to retake the House, and the loss of a coveted third-party line could prove the difference in what is expected to be a tight race.
“There are people who won’t vote on the Democratic line for ideological reasons, but they will vote for the same candidate on the W.F.P. line,” said Jennifer Cabrera, a leader of the party’s local chapter. “It’s a very real thing outside New York City.”
The Working Families Party and Mr. Jones have both rushed to contain the damage, as Democratic leaders and donors demand to know how the small but influential third party lost control of its ballot line and how Mr. Jones — who ran unopposed in the Democratic primary — failed to turn out even 200 W.F.P. supporters.
Mr. Jones and his allies insisted that the winner, Anthony Frascone, would have only a minor impact on the race.
“Notwithstanding Mike Lawler’s manipulation of the Working Families Party primary, Mondaire Jones is poised to defeat him as the Democratic nominee this fall in this district where registered Democrats outnumber Republicans by 80,000,” said Shannon Geison, his campaign manager.
A spokesman for the Working Families Party denounced Mr. Frascone, who defeated Mr. Jones by 19 percentage points, as a Republican plant who had no real relationship or commitment to the party’s progressive platform. He said the W.F.P. would not promote his campaign this fall.
“Mr. Frascone is not our endorsed candidate and we reject Lawler and the G.O.P.’s efforts to dupe voters,” said the spokesman, Ravi Mangla.
Republicans, on the other hand, were predictably celebratory. Mr. Lawler won his seat in 2022 by fewer than 2,000 votes, beating the chairman of House Democrats’ campaign arm, and needs all the help he can get.
A former professional political operative, Mr. Lawler has tried to distance himself from Mr. Frascone’s candidacy. His spokesman, Chris Russell, accused Mr. Jones of “trying to point the finger at anyone other than himself for his primary loss.”
But the fingerprints of Mr. Lawler and local Republican leadership are all over it.
Brett Yagel, a former local Republican mayor allied with Mr. Lawler, collected the signatures to get Mr. Frascone on the primary ballot. Lawrence Garvey, the chairman of the Rockland County Republican Party and a close confidant of the congressman, has long represented Mr. Frascone in legal matters, including defending his recent campaign in court.
Mr. Frascone, a bankrupt construction executive and former registered Republican, does not appear to have run a campaign by any conventional measure himself. He has no political website or social media.
Neither he nor Mr. Garvey responded to calls and text messages seeking comment.
Once Mr. Frascone was on the ballot, Republicans quietly turned their attention to improving his odds.
In early June, Rafi Silberberg, Mr. Lawler’s district director, wrote to a group of several hundred Orthodox Jewish supporters of the congressman, asking anyone who was not already registered to vote to contact him, according to messages reviewed by The New York Times.
In the weeks that followed, about 200 members of Rockland County’s Orthodox enclave, a generally conservative community that staunchly supports Mr. Lawler, enrolled in the Working Families Party. The registration drive, first reported by Gothamist, was large enough to exert sway in a region where the party counts fewer than 2,000 members.
Mr. Lawler and his allies would hardly be the first New York politicians to try to interfere in an opponent’s backyard.
New York is one of the only states in the country that allows candidates to run on multiple ballot lines. The practice, known as fusion voting, allows candidates to attract voters who might be disillusioned with the two major parties. (Mr. Lawler, for instance, will appear on both the Republican and Conservative Party lines.)
But it has also given rise to pranksterism, especially in New York’s politically fickle Hudson Valley. Just last week, Republicans also successfully nabbed the W.F.P. line from a Democrat running for State Senate there. And in a neighboring State Senate district, Democrats helped deny a Republican candidate the Conservative Party line.
What made the congressional race so different — on top of the stakes — was that rather than locking arms to repel the looming threat, Mr. Jones and the W.F.P. went to war.
It started when Mr. Jones gave an interview to The New York Times endorsing Mr. Bowman’s primary opponent, George Latimer, because of disagreements about the Israel-Hamas war. Party leadership was campaigning hard to save Mr. Bowman in the contentious race and viewed Mr. Jones’s harsh criticism as an egregious betrayal of one progressive by another.
The party’s state leadership team voted to pull all financial and organizational support for his race, though it did not formally rescind its endorsement.
Mr. Lawler moved quickly to exploit the opening, dispatching mailers to Working Families Party members that fanned the flames.
“Mondaire Jones threw Jamaal Bowman and WFP under the bus!” read one of them. Another said he had “backstabbed” Mr. Bowman and “attacked progressive leaders in New York.” It featured a photo of Mr. Jones and Representative Alexandria Ocasio-Cortez of New York torn down the middle.
Mr. Jones bought his own mailers and digital ads to try to counter the messaging, warning that “MAGA Republicans are trying to steal the Working Families Party line.”
The party sent a letter to all of its local members in mid-June stating that Mr. Frascone was “a plant by our political enemies,” though it did not mention Mr. Jones by name. In addition to texts and calls, the group hired an organizer to try to warn voters in person.
But it was too little, too late. Party leaders were consumed in an all-out campaign to save Mr. Bowman.
Top Democrats, who often bristle at the W.F.P. for backing liberal challengers to their candidates, were nonplused. “The W.F.P. was too busy messing around in Democratic primaries to worry about their own line being stolen by the Republicans,” said Jay Jacobs, the chairman of the state Democratic Party.
But Working Families Party officials said they had encountered another, bigger problem: Potential voters they reached said they felt scorned by Mr. Jones and unmotivated to vote in the contest.
In a race with just 482 votes, all of it probably made a difference. Only 81 votes were cast in Mr. Jones’s home county of Westchester, while 373 came from Rockland County, many of them from heavily Orthodox areas and the vast majority for Mr. Frascone.
Kirsten Noyes contributed research.