Representative Cullen was elected to the 13th Assembly District on May 1, 1990 in a special election to fill a vacancy. He has been re-elected to the Assembly since November, 1990.  Representative Cullen currently serves as the Chair of the Assembly Committee on Insurance.  He is also a member of the Assembly Committees on Education Reform, Colleges and Universities, Judiciary and Ethics, and the Joint Committee on Tax Exemptions.  Additionally, he has been a member of the Commission on Uniform State Laws since 1999.

Representative Cullen was elected to the Milwaukee School Board in 1983 and served continuously until 1990. He was President of the School Board from 1987 until 1990.

Representative Cullen is also an attorney, having practiced law for six years prior to being elected to the State Assembly. He received his law degree from Marquette University in 1984 and is a member of the Wisconsin Bar Association. He received his Bachelor of Science degree in secondary education  from the University of Wisconsin-Madison in 1981.

Representative Cullen is married and has two children: Eddie, who attends Rufus King High School, and Katie, who attends the Milwaukee School of Languages