The group includes moderates and senators known for crossing party lines, a few who are retiring and some who had already broken with their party to support same-sex marriage.
Proponents of the legislation argued that Congress needed to be proactive in ensuring a future Supreme Court would not invalidate same-sex marriages around the country.
Democrats made the same-sex marriage bill one of their first major agenda items in the postelection session, moving quickly to enact it while their party still controls both chambers.
Democrats made the same-sex marriage bill one of their first major agenda items in the postelection session, moving quickly to enact it while their party still controls both chambers.