This week, the four Republican state senators who provided the decisive votes to pass the marriage bill are to get a big financial boost from those donors, including Mayor Michael R. Bloomberg. A fund-raiser planned for Thursday night in Manhattan is expected to raise about $1.25 million to help finance their re-election bids next year.

The senators have come under heavy criticism from conservatives since they cast their votes in June. A national group that opposes same-sex marriage has purchased billboards in each of their districts, vowing to unseat the lawmakers, and the senators have been eagerly raising money in an effort to defend themselves against possible challengers.