“Certainly we want to keep the pressure on,” said the Rev. Jason J. McGuire, legislative director of New Yorkers for Constitutional Freedoms. Mr. McGuire’s organization is planning a rally in Albany for its supporters in June, and he added that he would continue meeting with senators in the hope of persuading them to vote against same-sex marriage.

“We all understand  both sides of the issue  that this fight is going to continue in the State Senate,” he said.

The Conservative Party is also applying pressure: it has threatened to strip its party affiliation and its ballot line from any politician who votes for same-sex marriage.

“We can’t look the other way,” said Michael R. Long, the party’s chairman, who added that he had informed the Republican leaders of the Senate and the Assembly of his threat to take away the Conservative ballot line  which in some elections can mean the difference of thousands of votes  from anyone who votes yes on the bill.

“We’re going to work as hard as we can in the next few weeks,” he said. “We intend to do everything we can possible with phone calls, memos, press releases, having our members call senators.”

Despite the conservative pressure, two Republicans spoke on Tuesday about why they dropped their opposition to granting same-sex couples the right to marry. Three Democrats who voted no in 2007 switched their votes to yes.

“There’s that little voice inside of you that tells you when you’ve done something right, and when you’ve done something wrong,” said Fred W. Thiele Jr., a Republican who represents the Hamptons. “That vote just never felt right to me. That little voice kept gnawing away at me.”