A spokesman for the Senate Democrats, Mike Murphy, said there was “no legislative proposal” to end fusion voting and that the “Senate majority has been clear that we support efforts to empower voters and strengthen New York’s democracy.”

By day’s end, nearly two dozen Democratic senators, in a letter to the Democratic leader, Senator Andrea Stewart-Cousins, said that abolishing fusion voting was a bad idea. They also called on Ms. Stewart-Cousins to decouple any negotiation over fusion voting from the budget, due April 1, when Mr. Cuomo could have some leverage over lawmakers. “The policy debate is too important to New York voters to be left to the 11th hour,” the letter read.

On the other side of the Capitol, the Democratic speaker of the Assembly, Carl E. Heastie of the Bronx, was more circumspect, saying he and his conference had not yet discussed the issue.

Fusion voting helps facilitate the survival of parties like the Conservative Party and the Independence Party, which often endorse Republicans. Under state law, any party which receives 50,000 votes in a gubernatorial election is guaranteed a spot on the ballot for the next four years.

Mr. Cuomo collected votes on four different ballot lines, including the Working Families Party, on the way toward a record vote-tally in November. But the W.F.P. did not endorse Mr. Cuomo in the primary; party leaders, saying they wanted to support a “real Democrat,” chose Ms. Nixon.

The W.F.P.’s bet backfired when Mr. Cuomo badly defeated Ms. Nixon in September, and the group subsequently endorsed Mr. Cuomo in the general election in a humbling reversal. Since then, the party has anticipated retribution from Mr. Cuomo, who has been known to hold a grudge.

The W.F.P. continued to issue warning shots to the Democratic Party in the last several days, sending out a battery of letters from supporters of fusion voting — including Senators Chuck Schumer, Kirsten Gillibrand, and most of the state’s Democratic House of Representatives delegation — and issuing multiple online pleas for support tagged with #StandWithWFP and #NoFusionBan.