Warren, 30, is chief legislative assistant to state Sen. Lisa Boscola, D-Northampton. Warren will step down from the city's Zoning Hearing Board, which he served on since May 2006.
This year's election focused on three main issues: the Police Department, finances and economic development.
The three winning candidates all said they support Police Chief Larry Palmer and will find ways to hire more officers to the full complement of 64.
The winners also agree a full-time finance director would help collect more than $1 million in unpaid debts.