When incumbent Joseph Vukovich was appointed to a judiciary position in 1997, Hagan was chosen to succeed him in the Ohio Senate. He was appointed to the State Senate on February 12, 1997, to represent the 33rd district in northeastern Ohio, centered on the city of Youngstown. During his time in there, he was chosen by the Senate Democratic caucus to serve as assistant minority whip in the 126th Ohio General Assembly; however, he stepped down from his leadership post when he entered the election for State Representative.