This post has been updated with comments from Petersen.
Sen. Branden Petersen, R-Andover, announced on Twitter today that he is not running for re-election.
"After a year of thought, I'm announcing that I will not be seeking re-election to the Senate. Time for family and making a living," he wrote.
Petersen has three young children, ages 4, 3 and 11 months.
Petersen joins Sen. Julianne Ortman, R-Chanhassen, and Sen. David Brown, R-Becker, in not seeking re-election, which could complicate efforts by Republicans to take the Senate in 2016.
Republicans have high hopes to take the upper chamber, given a number of DFL districts that lean Repubican, as well as chaos in the DFL caucus, with a bloc of mostly metro-area Senators questioning the leadership of Majority Leader Tom Bakk.
Petersen, who was elected when he was 24, said in an interview that the the all-consuming demands of the Legislature were causing him to miss important events in his family life and the lives of his young children.
He also said his professional life was constrained by the Legislature. He currently sells cars at an Elk River dealership but had previously been in retail management.
Petersen, who voted in favor of gay marriage, said he expected a Republican primary challenge, but he said he would have prevailed had he decided to run again.
Petersen said his biggest disappointment in the Legislature was an unwillingness on the part of colleagues to act independently.
"When the rubber meets the road, group psychology is pretty powerful and plays itself out in ways that I think don't always serve the interests of the constituents," he said.