Nearly half of all U.S. Democratic senators support an effort to add marriage equality to the 2012 Democratic Party Platform, gay weekly The Washington Blade reported.

Last month, Freedom to Marry launched the Democrats: Say I Do campaign, which calls on the Democratic National Committee (DNC) to endorse marriage equality in this year's platform. The DNC will ratify the document during its national convention, which begins September 3 in Charlotte, North Carolina.

The effort has been endorsed by seven Obama for America co-chairs and House Minority Leader Nancy Pelosi.

Twenty-two senators expressed support, including Michael Bennet of Colorado, Chris Coons of Delaware, Dianne Feinstein of California, Barbara Mikulski of Maryland, Ron Wyden of Oregon, Ben Cardin of Maryland, John Kerry of Massachusetts, Carl Levin of Michigan, Jeff Merkley of Oregon, Patty Murray of Washington, Mark Udall of Colorado, Jeanne Shaheen of New Hampshire, Frank Lautenberg of New Jersey, Chuck Schumer of New York, Tom Harkin of Iowa, Barbara Boxer of California, Kirsten Gillibrand of New York, Sherrod Brown of Ohio, Sheldon Whitehouse of Rhode Island, Richard Blumenthal of Connecticut, Bob Menendez of New Jersey and Al Franken of Minnesota.

Five senators, Murray, Levin, Mikulski, Lautenberg and Harkin, originally voted for the Defense of Marriage Act (DOMA), which bars federal agencies from recognizing the legal marriages of gay couples.