SALEM — Oregon’s Democratic co-speaker is running for the state Senate, giving up the potential to remain in his powerful House leadership position after the 2012 election.

Rep. Arnie Roblan of Coos Bay announced Thursday that he will seek the Senate seat now held by Democrat Joanne Verger, who is retiring. The expansive Senate district hugs the coast stretching from Tillamook to Coos Bay

The state House is evenly split between Republicans and Democrats, and Roblan has shared the speaker’s job with Republican Bruce Hanna of Roseburg.

Republican oral surgeon Scott Roberts is the only candidate who has filed to for the 5th District Senate seat.