ALBANY, N.Y. — Senators Bernie Sanders and Elizabeth Warren entered an unexpected clash on Tuesday with New York Democratic leaders over the fate of a progressive third party.
The dispute stems from a political flier paid for by the state party featuring Joseph R. Biden Jr., his running mate, Senator Kamala Harris, and Senators Warren and Sanders, all smiling and pleading with New Yorkers to vote “Democratic — all the way!”
But Ms. Warren and Mr. Sanders said they were not consulted about the flier, and had they been, they would not have consented to the ad, which pushes voters to cast ballots on the Democratic Party line.
Both senators support the Biden-Harris ticket, but want ballots cast for the candidates on the Working Families Party line, which has backed them in the past.
Mr. Sanders accused the state Democratic Party, which is effectively controlled by Gov. Andrew M. Cuomo, of trying to sabotage the Working Families Party.
“It is absolutely unacceptable for the New York Democratic Party, which just a few short months ago supported canceling the presidential primary, to now use my image in a push to punish the Working Families Party,” Mr. Sanders, an independent from Vermont, said in a statement.
“They never asked my permission and I wouldn’t have given it if they had,” he said. “I believe New Yorkers should vote for Joe Biden and Kamala Harris on the Working Families Party line.”
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That sentiment was echoed by Kristen Orthman, a spokeswoman for Ms. Warren, who said the Massachusetts senator “didn’t approve this ad” and asked that digital versions of it “be taken down.”
Under state law, candidates in New York can collect votes on several different party lines, a system known as fusion voting. But under a new law adopted this year, political parties in New York have to earn 130,000 votes — or 2 percent of the total vote — every two years in order to automatically retain their ballot lines. Parties that do not reach that threshold would have to petition for their candidates to appear.
State Democratic officials acknowledged that they did not seek permission from either senator, or the Biden ticket, to use their images, but defended the $357,000 campaign, which also included digital advertisements using images of Senators Warren and Sanders.
“My interaction with them is none,” said Jay Jacobs, the chairman of the New York State Democratic Committee and a longtime ally of Mr. Cuomo’s. “The entire piece simply speaks to voting for Democrats up and down the ballot.”
“My job is to get voters out to vote on the Democratic line,” he added. “And there’s nothing wrong with that.”
Mr. Jacobs said that the mailer and digital ads were meant to “increase down-ballot voting” for Democrats, some of whom do not appear on the Working Families line.
“I don’t see how Elizabeth Warren would be upset with that,” he said. “And I don’t see how, frankly, Bernie Sanders would be upset with that.”
Mr. Cuomo’s unpleasant history with the Working Families Party dates back several years, including a fraught nomination process in 2014. It reached a low point in 2018, when the W.F.P., which had been founded in the late 1990s and backed by various labor groups, chose to support Cynthia Nixon, the actress, in her challenge to Mr. Cuomo in the Democratic primary.
Some of those labor supporters fled, and Mr. Cuomo won the September primary easily after spending more than $20 million. He was subsequently elected to a third term, as the W.F.P. capitulated and gave the governor its line, where he received more than 114,000 votes.
In 2019, Mr. Cuomo announced the formation of a new commission to look into public financing of campaigns, albeit with an unusual caveat: The panel could also examine ballot eligibility levels for third parties, such as the W.F.P.
Third-party leaders feared that the governor intended to threaten their existence, and two parties — the Working Families Party and the Conservative Party — sued to challenge the commission’s authority. The parties’ fears were soon realized: In November 2019, the commission voted to increase the eligibility levels.
The parties won their lawsuit earlier this year, but the commission’s recommendations still went forward after being incorporated into this year’s budget deal.
In recent weeks, a roster of progressive lawmakers — including Senator Warren and Representative Alexandria Ocasio-Cortez of New York — have called on voters to cast ballots for Mr. Biden on the W.F.P. line: Row D. They note that those votes “count the same, to beat Trump.”
That message was voiced again on Tuesday at a Lower Manhattan rally attended by Senator Chuck Schumer of New York, the New York City public advocate, Jumaane Williams, and an array of state legislators.
Mr. Williams, who was Ms. Nixon’s running mate in 2018, was critical of the state party, saying it “would not have moved where it is as quickly as it did if it wasn’t for the Working Families.”
“There are only a few people who don’t want you to vote on the Working Families line,” Mr. Williams said. “Conservatives, Republicans and Gov. Andrew Cuomo.”
Mr. Cuomo has steadfastly denied any ulterior motives regarding the W.F.P., and, on Tuesday, a spokesman for Mr. Cuomo’s office declined to comment on the advertising campaign.
But Mr. Jacobs said he found it striking that “with a week to go in the most consequential election in our history, the W.F.P. is worried about itself.”
“The W.F.P. has a self-image problem,” said Mr. Jacobs. “Everything’s about them.”
Juliana Kim contributed reporting from New York.