Senate Finance Committee Chairman Max Baucus, D-Mont., announced Tuesday that he will not run for re-election in 2014, putting another Senate seat in play.

Elected in 1978 after two terms in the House, Baucus will finish his sixth term. He is 71 and is Montana's longest-serving senator ever.

“Serving the people of Montana has been the greatest honor and privilege of my life," he said. “... When I first asked my hero and mentor Mike Mansfield whether I should run for U.S. Senate nearly 40 years ago, he told me it would take a lot of hard work, a lot of shoe leather, and a bit of luck. In the next year and a half, I want to spend all my hard work, shoe leather and luck working for the people of Montana instead of on campaigning.

“So, after much consideration and many conversations with my wife Mel and our family, I have decided not to seek re-election in 2014. I will serve out my term, and then it will be time to go home to Montana.” 

Former Gov. Brian Schweitzer, who just left office after two terms, is the Democrats’ best hope for holding the seat. After Baucus made his announcement, Schweitzer told The Hill he will consider a run but won't decide until after May 2.

"I'm the kind of guy that, when I see a broke-down pickup, I'll get out with my tools and try to fix it, and I can tell you looking at Washington, D.C., from Montana, there is no bigger broke-down pickup than the Senate in Washington, D.C.," Schweitzer said.

The former governor said he was "focused like a laser" for the next 10 days on helping the Stillwater Mine, a major Montana project he's working to help turn around, and would turn his focus toward a possible Senate bid afterwards.

"I'm not ruling anything out, or anything in, but I can tell you right now I'm focused like a laser … I'm focused on the mine, on climbing that mountain," Schweitzer said. 

"Then I'll take a deep breath; I'll take a look around. And when you're standing on a mountain in Montana, you can see a long ways."

Schweitzer remains popular in the state. His approval rating was 56 percent in a February survey from Public Policy Polling, with 37 percent disapproving. 

Baucus has been feuding with the Senate Democratic Caucus and Majority Leader Leader Harry Reid, D-Nev., over tax policy and gun control, Politico notes.

In an interview with Politico Tuesday, he downplayed his splits with fellow Democrats, and he said they had “nothing to do” with his decision to retire, calling the fights a “curious combination of events.” Free of re-election pressures, Baucus said he wants to focus on overhauling the tax code before embarking on a new career in 2015.

“I’m now 71,” Baucus said. “You don’t need to be a rocket scientist that if I run and win and finish my next term, I will be close to 80. That kind of limits my opportunity to be able to do things outside of the Senate.”

Still, the Montanan’s colleagues were stunned by his decision, given that he had maintained an aggressive fundraising schedule and was a long-standing fixture in the halls of the Senate and his home state. Democrats gave him two standing ovations during a closed-door lunch Tuesday.

“It was a shock,” said Sen. Jon Tester, D-Mont., who learned of Baucus’ decision Monday night.