Stephen Kerrigan has won the three-way Democratic primary for Massachusetts lieutenant governor.

The former Lancaster selectman previously served as a top aide to the late U.S. Sen. Edward Kennedy, and later as chief of staff to former Attorney General Tom Reilly.

He defeated Mike Lake and Leland Cheung in Tuesday's voting.

Kerrigan will team with Democratic gubernatorial nominee in the November election.

Kerrigan said he sees the lieutenant governor's office as a place where constituents can go for help in navigating state government regulations. The office has been vacant since the resignation of Timothy Murray last year.

Former state Rep. Karyn Polito was the only Republican candidate for the number two job and is teamed with GOP gubernatorial nominee Charlie Baker in November.