Rep. Tammy Baldwin (D-Wis.) announced Tuesday that she'll run for Senate in 2012, making her candidacy official in a Web video.
Baldwin, who's been exploring running to succeed the retiring Sen. Herb Kohl (D), positioned herself as a "progressive fighter for Wisconsin," and a candidate who would govern in the mold of Kohl and former Sen. Russ Feingold (D-Wis.).
She enters the race as the early front-runner for the Democratic nomination. Feingold passed on an opportunity to regain a seat in the Senate, and liberal activists have been enthusiastically supportive of Baldwin's candidacy since Kohl announced his retirement.
On the Republican side, former Gov. Tommy Thompson (R) has been exploring running for the seat, though conservative activists have expressed their doubts about his bona fides. Former Rep. Mark Neumann (R-Wis.) is also running for the seat.