After months of championing only civil unions for gay couples - which she deemed a more politically viable step - O'Brien stood with some two dozen gay and lesbian political leaders in front of Old City Hall and said she would support gay marriage if the Legislature approved such a measure.

No state has legalized gay marriage, and O'Brien's remarks put her to the left of most national Democrats. But she stressed she was unlikely to be confronted with a gay marriage bill on her desk if she became governor, and that she would devote her efforts to passage of civil unions.