But they had to get the bill to the floor. This they couldn't do without Senate Majority Leader Dean Skelos. He controlled the chamber.
Like many of the Republicans, Skelos quickly left the chamber after the vote without talking to the media. His office didn't return several calls Saturday.
Skelos was the gatekeeper, they all knew, the one who could block legislation from ever being voted on, and everything would ride on a decision he would reach about a law he opposed.
"Getting it to the floor was everything," said Brian Ellner of Human Rights Campaign, one of the many gay-rights groups that was part of an effort over the last six months to get the historic legislation passed. "We felt that we had the votes, if we could just get it to the floor."
In the end, the activists were right. Once the measure hit the Senate floor, they won by almost the narrowest margin possible, 33-29.
The landmark victory for same sex marriage supporters has its roots in its defeat in the Senate in December 2009. Despite Democrats then controlling the chamber, a same-sex marriage bill went down in defeat, 38-24 -- opponents were all 30 Republicans then in the chamber and eight Democrats -- but that provided a road map for advocates.
"They [the advocates] wanted to be able to see who they needed to target, both Democrats and Republicans, because they understood then" that not all Senate Democrats would support it," said a person familiar with the negotiations.
From that point, based on interviews with numerous activists and officials, proponents point to four key steps to turn the legislation into law.
The first step toward passage was a quiet campaign to flip Democratic "no" votes. They were helped by the fact that several of the Democratic opponents were now gone, either voted out or, in one case, expelled. Months of effort - calls, polls, letters -- focused on three senators: Carl Kruger (D-Brooklyn), Joseph Addabbo (D-Brooklyn) and Shirley Huntley (D-Queens). It worked.
When the three senators announced two weeks before the end of the legislative session they would support same-sex marriage, that meant supporters had corralled 29 of the 30 Democrats (Sen. Ruben Diaz, D-Bronx, was never considered a possible switch) and they were just three votes from a majority.
The next step was to get a Republican to announce his support. That came days later when Rochester-area Sen. James Alesi said yes. He said he regretted voting no in 2009 but did so because the GOP had made a strategic decision to vote as a bloc. Now, he would vote his conscience. It broke the dam.
"I think what it did was help not kill it ahead of time" by showing that the GOP would not vote in a bloc this year, Alesi said. "I don't think it was about trying to take a risk or trying to be first. It was just something I thought I should do."
The next day, Sen. Roy McDonald (R-Saratoga) said he too would reverse his no vote. That then meant that exactly half of the state's 62 senators were publicly committed.
The third key step was getting the "religious exemptions" in the bill to protect churches and church-related agencies from discrimination claims. For two weeks, the governor and top staff met quietly with a handful of senators considered to be up for grabs. While noisy protests filled the third floor of the Capitol, home of the legislative chambers, secret meetings went on one floor below.
Sen. John Flanagan (R-East Northport) made such a trip as did Sens. Andrew Lanza (R-Staten Island), Stephen Saland (R-Poughkeepsie), Mark Grisanti (R-Buffalo) and Kemp Hannon (R-Garden City). Two of them would provide the deciding votes Friday.
Hannon made it known that he remained an opponent, but as an attorney and as a top GOP policy negotiator, he was asked to "lawyer" the confabs over language that included Lanza and Saland. Flanagan strove to hear all arguments but also voted no. Lanza clearly wrestled publicly, frequently granting interviews in which he'd say he thought he was a "no" but had made no final decision. He would stay a no.
Back-and-forth the drafts went, checking with the Assembly point man, Daniel O'Donnell (D-Manhattan). Sometimes better known as Rosie O'Donnell's brother, the lawyer had written the marriage bill and was open to changes that would make fence-sitters comfortable.
The amendment went through three drafts. Final changes included saying that a municipality couldn't override the religious protections, one that made the exemptions more explicit and one that said if one of the protections was struck down by a court, the entire statute would be voided.
Finally, the Republican conference provided the fourth step. Days earlier, a handful of members of the GOP old guard had reached a boiling point. They were upset that Republicans were even weighing the same-sex marriage issue, given that the overwhelming number of them were opposed. Rumors flashed around the Capitol that Skelos' role as leader might be challenged -- although numerous senators later strongly denied that feelings ever got that heated.
Some senators made a pitch: Offer a statewide referendum instead of acting legislatively. Let the public decide.
"I thought this was an issue of such magnitude that it should go out to referendum," Flanagan said. But that was shot down. The state's referendum process was such that even if the public approved, same-sex marriage would be several years away from becoming legal.
Republicans spent nearly eight hours behind closed doors. Not all of it was on this issue. There were last-minute negotiations on the tax-cap bill. At 5:30 p.m., Skelos issued a statement.
"After many hours of deliberation and discussion over the past several weeks," he said, "it has been decided that same-sex marriage will be brought to the full Senate for an up-or-down vote. . . . As I have said many times, this is a difficult issue and it will be a vote of conscience for every member of the Senate."
"Skelos could have been a dictator and just said no. But he didn't," Alesi said. "That's what makes him a strong leader."
In a victory news conference, Cuomo said it was politically dangerous for the Republicans who voted yes. Asked if it was similarly dangerous for Skelos to allow the vote, the governor said no.
"I think the senator did it because it was the right thing to do . . ." Cuomo said. "I don't know that there was a viable alternative to not bringing it to the floor because I don't think the people of the state would tolerate not having a vote. I think he handled it well."