Michael J. Sullivan, Jr. became Holyoke's mayor in 1999, defeating incumbent Mayor Daniel Szostkiewicz, whom Sullivan criticized for failing to deal with rampant corruption in the Holyoke Police Department and for allowing an expanded quarrying operation on Mt. Tom.

Before he became mayor, Sullivan worked as a sales and marketing executive with Burke Beverages, Inc. from 1981-1999. In 1990, Sullivan opened the High Street bar Nick O'Neill's, which he sold in 1998 as he prepared to run for mayor. His political career began in 1988 when he was elected to the Board of Aldermen.

Sullivan attended Holyoke Community College and Worcester State College but did not graduate. He is continuing his education through the University Without Walls program at UMass. Sullivan is married to Patricia Cauley Sullivan, an English professor at Holyoke Community College.

Earlier this year, Sullivan announced that he will not run for re-election when his fifth term in office expires in November, 2009. Sullivan did not rule out of the possibility of running for another elected office in the future.