Senate Republican leaders said on Wednesday that they had not decided whether to take a vote on legalizing same-sex marriage, as advocates were in a full-court press to gain the one vote needed to pass the measure before Monday, the scheduled end of this year's legislative session.

Thirty-one members of the 62-seat Senate have now publicly backed the legislation, including two Republicans who have emerged in recent days to say they would vote for same-sex marriage. The Republican-controlled chamber, where gay marriage was defeated two years ago by a wide margin, is seen as the last obstacle to the measure, which is strongly supported by Gov. Andrew M. Cuomo, a first-term Democrat, and has passed the Democratic-controlled State Assembly several times before.