"I didn't get my arm twisted by anybody on that. Because that's Montana," Baucus said. "I have a sign on my desk: 'Montana comes first.' "
Baucus infuriated Democratic colleagues in 2001, just ahead of a potentially tough re-election fight, when he worked with Republicans to write one of the largest tax cuts in American history just months after George W. Bush won the White House. In 2003, he helped Bush pass his Medicare prescription drug plan, but in 2005 he led the opposition to Bush's effort to partially privatize Social Security.
Baucus, 71, has spent most of his adult life in Washington, having been elected to the House in 1974 and to the Senate in 1978. He explained his decision to retire in squarely personal terms, saying he had been wrestling with the idea since his mother died just over a year ago.
"It made me realize I'm not immortal. We're all mortals," Baucus said. "I don't want to leave here when I'm 80 years old. There are things I want to do. . . . I want to see what life is like outside the United States Senate."
With more than $5 million already in his campaign war chest, Baucus had been aggressively raising funds for re-election in a state that gave Republican presidential nominee Mitt Romney a 13-percentage point victory in 2012.
"It's a big loss for the Senate," said Sen. Charles Grassley, R-Iowa, who drafted the 2001 tax cuts and the Medicare law with Baucus.
Baucus became the fifth Senate committee chairman, with more than 140 combined years of experience, to announce his intention to retire next year. The others include John Rockefeller IV, D-W.Va., 75, chairman of the commerce committee, and Tom Harkin, D-Iowa, 73, chairman of the health committee. In recent years, longtime committee chairmen Robert Byrd, D-W.Va., Daniel Inouye, D-Hawaii, and Edward Kennedy, D-Mass.. died in office.