Democratic Party chairs from eleven states on Thursday endorsed adding gay marriage to the 2012 Democratic platform.

Calling for the inclusion are John Burton of California, Joan Wagnon of Kansas, John Walsh of Massachusetts, Ken Martin of Minnesota, Jon Wisniewski of New Jersey, Jay Jacobs of New York, Meredith Wood Smith of Oregon, Boyd Richie of Texas, Jake Perkinson of Vermont, Dwight Pelz of Washington and Mike Tate of Wisconsin.

They join a growing chorus of Democrats who have endorsed putting marriage equality in the platform, including Democratic National Convention chair Antonio Villaraigosa, House Minority Leader Nancy Pelosi, U.S. Senate candidate Elizabeth Warren and nearly two dozen U.S. senators.

Freedom to Marry launched its Democrats: Say I Do campaign with the goal of adding marriage equality to the Democratic platform in March.

“Nearly a year ago, New Yorkers stood united in supporting full marriage equality for all loving and committed families, and Democrats led the way,” New York Democratic Party Chair Jay Jacobs said in a statement. “We now see first-hand how marriage improves the lives of gay couples and their families, and strengthens businesses and communities throughout the Empire State. Marriage equality is simply the right thing to do, and that's why I strongly believe that the Democratic Party should stand united for a freedom to marry plank in our national Democratic Party platform.”

Nearly 40,000 Democrats have added their names to Freedom to Marry's Democrats: Say I Do online petition.