When members of the now-defunct Independent Democratic Conference reunited with mainstream Democrats in the New York State Senate in early April, they probably hoped that their fledgling primary challengers would fade.
In the three months since, that has not happened.
Instead, there are increasing signs that those challengers are making inroads with members of the state’s political establishment and with local leaders in the districts they hope to represent. And in many cases, endorsements are being driven by the I.D.C.’s past association with Republicans, with whom it collaborated to help that party maintain control of the State Senate for more than seven years.
The latest example will come on Thursday, when four Assembly members from central Brooklyn will endorse Zellnor Myrie, a 31-year-old Democrat who is challenging Senator Jesse Hamilton, who defected to the I.D.C. in late 2016, saying he wanted to “get results.” That decision — either pragmatic or opportunistic, depending on your worldview — now seems like it could come back to haunt former I.D.C. members like Mr. Hamilton and his peers.
“We need progressive public servants in our State Legislature,” said Assemblyman Walter T. Mosley, one of the four lawmakers endorsing Mr. Myrie, in a statement that characterized the I.D.C. as a “broken model of political expediency and self-interest.” “Zellnor Myrie is that leader.”
In Queens, meanwhile, another Assembly member, Arevella Simotas, intends to endorse another young challenger on Thursday: Jessica Ramos, 33, who is running to unseat Senator Jose Peralta, who also left the mainstream Democrats to join the I.D.C. last year.
“Jose Peralta betrayed Queens,” Ms. Simotas said on Wednesday, “while Jessica Ramos will fight for women, students and affordable housing.”
In both Mr. Zellnor and Ms. Ramos’s cases, most of the lawmakers endorsing them have Assembly districts that overlap the contested Senate districts. But some I.D.C. challengers have also been picking up support of major labor groups like Service Employees International Union, Local 32BJ, whose president Hector J. Figueroa said on Twitter on Sunday that the “ones to be blamed are I.D.C. incumbents themselves & those STILL defending them.”
“I.D.C. betrayed voters, creating a big political mess,” Mr. Figueroa wrote. “Time to clean up.”
Last week, the union endorsed Alessandra Biaggi, 32, who is running to try to unseat Jeffrey D. Klein, who led the I.D.C. and is currently the No. 2 Democrat in the Senate, behind Andrea Stewart-Cousins, of Westchester County, who has long been the leader of the mainstream conference.
The most hard-fought I.D.C. races seem to be occurring in New York City and its suburbs, and here, too, some prominent Democrats are siding with the newcomers, including the City Council speaker, Corey Johnson, who endorsed four I.D.C. challengers on the steps of City Hall in late June. Mr. Johnson’s endorsements came just days after the surprise primary win of Democratic newcomer Alexandria Ocasio-Cortez over longtime Representative Joseph Crowley, a political ally, though he denied the two events were related.
On Tuesday night, Mr. Johnson spoke at an event for Ms. Biaggi and hammered Mr. Klein’s former group. “It feels really good to tell the truth, and for too long, people were not telling the truth about the I.D.C. and the damage that they’ve done to the state of New York,” Mr. Johnson said. “And that damage was all in their own self-interest.”
The former I.D.C. members aren’t exactly rolling over, however. By the end of last week, Mr. Klein answered that endorsement with one of his own from Local 1199 of the Service Employees International Union, the state’s largest union.
Barbara Brancaccio, a spokeswoman for the former I.D.C. members who are being challenged, cited a raft of other endorsements from labor and other groups and leaders received by Mr. Hamilton, Mr. Klein and Mr. Peralta, and noted that the primary challengers and their supporters “are working overtime to divide and dismantle the Democratic Senate they claim to want to protect.”
“These so-called reformers, instead of working for a united Democratic Senate, are targeting true Democrats and aiding and abetting the Republicans in New York State,” she said.
Mr. Klein also recently sent a mailer to constituents in his district, which includes parts of the Bronx and Westchester County, depicting himself and Gov. Andrew M. Cuomo — who is also up for re-election this year — standing side-by-side smiling. “Together,” it reads, “we can accomplish even more.”
Mr. Cuomo’s relationship with the I.D.C. — which formed shortly after the beginning of his first term in 2011 — has also been a potent talking point for Mr. Cuomo’s primary opponent, Cynthia Nixon, who campaigned with several of the challengers on Tuesday, rallying in Union Square in support of abortion rights. At that rally, she said that Mr. Cuomo had “prioritized supporting the I.D.C.” over passing bills to protect women’s reproductive rights. (Mr. Cuomo’s office called Ms. Nixon’s criticism “self-serving election year games.”)
Mr. Cuomo, 60, seemingly has much riding on Democratic efforts to retake the Senate, repeatedly calling it a priority in this year’s elections; Democrats are currently a single vote short of taking control of the 63-seat house.
And on Wednesday, his campaign reiterated that sentiment, while taking a swipe at past efforts to unite Democrats as well as President Trump’s “destructive, ultra-conservative agenda.”
“For over a decade the Senate Democratic Conference has been dysfunctional and fractured,” said Abbey Fashouer, a campaign spokeswoman. “The governor supports Democratic unity and is 100 percent focused on growing the Democratic majority in the Senate by picking up seats.”
In April, the governor sat at a table in his Midtown office to announce a détente in the schism between Mr. Klein and Ms. Stewart-Cousins, saying “we are uniting the Democratic Party to fight a common enemy for the greater good.”
How real that unity was, however, has been an open question for months, as some members of the mainstream Democrats have only warily welcomed the former I.D.C. members back into their conference. During its seven years in existence, one of the most outspoken critics of Mr. Klein’s group was Senator Michael Gianaris of Queens, who was supplanted by Mr. Klein as deputy minority leader.
Mr. Gianaris has said he wants nothing more than a Democratic-led Senate. But in an interview on Wednesday, he indicated that didn’t necessarily mean throwing his support behind the eight members of Mr. Klein’s old group.
“I will not be supporting,” he said, “any of the former I.D.C. members.”