From 1965 to 1972 he was a member of the Massachusetts House of Representatives. In 1972 he ran for the Massachusetts's 5th congressional district seat vacated by F. Bradford Morse. He finished second in the nine candidate Democratic primary, losing to John Kerry 27.56% to 20.75%.[2] From 1971 to 1973 he served as director of the Lowell Bank and Trust Co.[3]
In 1974, Sheehy was named city manager of Lowell.[4] He resigned his post on September 5, 1975, after he was convicted of bank fraud and three counts of making false statements in Lowell Bank and Trust Co.'s books.[3] He was sentenced to 60 days in prison and lost his license to practice law.[3][5]