The Massachusetts Democratic Party (MassDems) is the affiliate of the Democratic Party in Massachusetts. It is chaired by Steve Kerrigan and is the dominant party in the state, controlling all nine of the state's U.S. House seats, both U.S. Senate seats, all six elected statewide offices including the governorship, and supermajorities in both houses of the state legislature.

Stephen "Steve" Kerrigan is an American political executive who has served as the chair of the Massachusetts Democratic Party since April 2023 and was the Democratic nominee for Lieutenant Governor of Massachusetts in the 2014 election. From 2003 to 2007, Kerrigan served as chief of staff to Massachusetts Attorney General Thomas Reilly, and from 2009 to 2012, CEO of the Democratic National Convention. Kerrigan was also president of the 2013 Presidential Inaugural Committee.