Democrat Ernie Wittwer is running for the state Senate in the southwestern Wisconsin district currently held by Republican Sen. Dale Schultz.
Wittwer announced his candidacy Tuesday in the Capitol outside the Senate chamber. Schultz is a moderate Republican who has not announced yet whether he will seek re-election.
Schultz has angered many in his party for a series of votes against Gov. Scott Walker's collective bargaining proposal, Walker's state budget this year and a bill making it easier to open a mine in northern Wisconsin.
Conservative Republican Rep. Howard Marklein is also running for Schultz's seat.
Schultz's campaign spokesman Todd Allbaugh says Schultz is considering running for the seat as an independent. Allbaugh says Schultz is still deciding whether to seek re-election.