As a landmark gay marriage bill hurtled toward an uncertain vote last year, New York’s Democratic leaders scrambled to corral support. Gov. David A. Paterson delivered impassioned speeches, Senator Kirsten E. Gillibrand headlined a giant rally and City Council Speaker Christine C. Quinn shuttled back and forth to Albany to lobby lawmakers.

But the state’s most popular Democrat, Attorney General Andrew M. Cuomo, was all but invisible.

He was asked by those pushing for the measure to call three wavering senators. He never spoke with two of them, their aides said, and did not reach another until after the senator had voted  against the bill.

“He left a message,” said a spokesman for Senator Joseph P. Addabbo Jr., a Democrat from Queens, who finally spoke with Mr. Cuomo after the vote.

In the end, none of the three senators supported the bill.

Mr. Cuomo, 52, appears poised to succeed the most pro-gay rights governor the state has ever had, at a pivotal moment in the debate over same-sex marriage, and with gay men and lesbians exercising increasing influence within the state Democratic Party.