Rep. Barney Frank (D-Mass.) won't be challenging Sen. Scott Brown (R-Mass.) in 2012.
Frank said Thursday he'll seek reelection to his House seat next year, meaning he'll pass on a Senate run.
Frank, the 15-term Democratic stalwart, is fresh off of one of the stiffest reelection challenges of his career in 2010.
The congressman had been eyed by party leaders as a possible candidate to challenge Brown in 2012 in one of the most prominent Senate races. Frank had considered, but passed on, running in the special election last year in which Brown emerged victorious.
"While I would have preferred to put off a discussion about the next election until a later date, I have been asked on a number of occasions about my plans," he said. "In addition, I have become convinced that making my decision to run for reelection known is important for maximizing the impact I can have on the range of issues to which I am committed."
Republicans made Frank's campaign competitive last year, despite his district being solidly Democratic. Republican Sean Bielat had made waves with his fundraising and national media profile, raising hopes among GOP voters that he might beat Frank, who's often targeted by conservatives.
Frank ultimately pulled off a healthy 54-43 percent victory. His reelection effort in 2012 is considered to be a safer endeavor because his eventual challenger won't have the benefit of the GOP headwinds that helped many Republican candidates in 2010.
-- This post was updated at 10:26 a.m.