Massachusetts is getting another senator with Am Law 200 ties.

William “Mo” Cowan, who became a senior adviser to Massachusetts Governor Deval Patrick in 2009 after spending 12 years as a litigation partner at Mintz, Levin, Cohn, Ferris, Glovsky and Popeo in Boston, has been tapped by Patrick to replace newly minted U.S. Secretary of State John Kerry until a special election is held in June.