U.S. Rep. Matt J. Salmon stressed opposition to same-sex marriage during interview with a Phoenix television station.
Lawmakers approved the bill by a 23-8 vote margin.
Kirk becomes second sitting Republican in the upper house to do so
Announcement coincides with expected introduction of bill to allow gays to tie the knot in Delaware
Tyler, Olson filed first lawsuit to challenge ban in 2004
Measure is widely expected to pass
Whitman-Walker Health, Casa Ruby among groups that took part in the event
Only eight Senate Democrats have yet to publicly endorse nuptials for gays and lesbians
Anti-trans policy established in 1981
But Ariz. senator says opposition to gay nuptials won't change