Mass. Democratic Chairman John Walsh Stepping Down

The head of the Massachusetts Democratic Party is stepping down after holding the post since 2007.

John Walsh twice helped Deval Patrick win the governor's office and put together the political organization that helped propel Elizabeth Warren into the U.S. Senate last year.

Walsh's biggest defeat as chairman came in 2010 when Republican Scott Brown defeated Democrat Martha Coakley for the U.S. Senate seat left vacant by the death of longtime Democrat Edward Kennedy.

Walsh will join the Democratic candidates who competed in the 5th Congressional District primary for a unity event in Waltham Thursday night before handing the chairmanship to his presumed successor, state Sen. Thomas McGee.

State Sen. Katherine Clark won the Democratic primary.

Walsh isn't leaving politics, however. He's set to become executive director of Patrick's political action committee, the Together PAC.