First sitting Md. Governor to appear at gathering
Mention comes one day after Senate testimony in favor of the bill
Same-sex marriage and gender identity nondiscrimination legislation both being pushed
President says "I could not be prouder of our endorsement"
Predicts the Md. marriage bill will fail
3,000 LGBT activists attended one of the largest annual LGBT conferences in the nation
bill introduced on Jan. 17
Maryland Corporate Council made its official debut Jan. 19
Announcement made at rally sponsored by largest Maryland labor unions
poll finds 49 percent favor same-sex marriage