They write on their site:
This has been a big couple of weeks in the fight for the freedom to marry for same-sex couples. Yesterday, Washington became the seventh state to stand up for the fundamental right of same-sex couples to marry. And last week, a three-judge panel of the Ninth U.S. Circuit Court of Appeals ruled Proposition 8 unconstitutional. We know where the GOP frontrunners stand on marriage for gay couples—it’s not pretty—that’s why we need the support of a critical player: President Obama. As the leader of the most LGBT friendly administration in history, we need him to lead on this issue too.
Hit the link to add your name to their letter to the president.