Max Baucus talks with reporters on Capitol Hill. (AP Photo/Susan Walsh)

Montana Senator Max Baucus, a Democrat who frequently clashed with his party’s economic populists as the Wall Street–friendly chairman of the Senate Finance Committee, will step down at the end of his current term.

Baucus, who will retire from the Senate after thirty-six years, played a critical role in the health-care debate that led to the enactment of the Affordable Care Act. Given substantial responsibility by the White House, the Montana senator declared that “single payer was not an option on the table.” That drew the ire of activists, who charged that Baucus was tipping the balance in favor of the insurance and pharmaceutical industries, and Finance Committee hearings grew so contentious that the chairman ultimately ordered protesting doctors and nurses removed.

A New York Times profile of Baucus later reported: “He conceded that it was a mistake to rule out a fully government-run health system, or a ‘single-payer plan,’ not because he supports it but because doing so alienated a large, vocal constituency and left Mr. Obama’s proposal of a public health plan to compete with private insurers as the most liberal position.”

The senator frequently split with progressive Democrats on critical issues. For instance, he voted to authorize President Bush to attack Iraq and provided high-profile support to President George W. Bush’s tax cuts in 2001. A frequent defender of corporate tax breaks, he was criticized for his tepid response to efforts to crack down on abuses of overseas tax haven. In 2005, he opposed repealing the tax subsidy for US corporations that offshore manufacturing operations.

Baucus, who sided with the US Chamber of Commerce 64 percent of the time in the group’s 2011 survey of Senate votes, often parted with organized labor on free-trade issues. Famously, after the senator wrote a 2007 Wall Street Journal opinion piece arguing that his party should work with former President George W. Bush to renew so-called “fast-track authority” for negotiating international trade deals—a move that limits the ability of Congress to check and balance the executive branch—the Montana State Senate (which was controlled by Democrats) voted 44-6 in favor of a resolution that urged Congress “to create a replacement for the outdated fast track system.” Montana’s other Democratic senator, Jon Tester, pointed declared that he was “against fast-track.”

Baucus and Tester split again this month on the question of adopting gun-purchase background checks. Baucus voted “no,” while Tester voted “yes,” explaining, “Common-sense measures that protect our Second Amendment rights while making our families safer deserve our support.”

As the gun vote approached, the national Progressive Change Campaign Committee launched an ad campaign urging Baucus to vote “yes.” Despite the fact that a poll commissioned by Mayors Against Illegal Guns found that 79 percent of Montanans backed background checks for guns sales, Baucus pushed back, arguing that the “top-down, one-size-fits-all approach like the president is pushing simply won’t work for us in Montana, and I won’t support it.”

Ultimately, however, it was on the economic issues that critics scoured Baucus upon his announcement that he would step down after this term. “Good bye, Senator K Street,” said PCCC co-founder Stephanie Taylor, referencing the DC base of many special-interest lobbyists. According to a recent New York Times report, at least twenty-eight former Baucus aides have become lobbyists on tax issues that are often addressed by the Finance Committee.

“Max Baucus has a history of voting with corporate interests and not the interests of Montana voters—taking millions from Wall Street, insurance companies, and lobbyists,” continued Taylor. “Montana will finally have a chance to have a senator with its best interests at heart, and we hope Brian Schweitzer jumps into the race immediately.”

Schweitzer, a popular former governor, tops lists of prospective Democratic contenders to replace Baucus. Distinct from the retiring senator in style and on many policy matters, Schweitzer several years ago proposed establishing a single-payer healthcare program in Montana. And he’s been a loud proponent of “Buy American” proposals that aren’t particularly popular with advocates of free trade.

Pitched as a 2016 Democratic presidential prospect, Schweitzer acknowledged Tuesday that he is seriously considering the Senate race. He came on the Montana political scene in 2000 as an upstart candidate who narrowly missed unseating Republican senator Conrad Burns.

Now, says Schweitzer, “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.”

Montana is not much of a swing state in presidential politics, but populist Democrats have run well there in recent years, winning the governor’s office in the past three elections.

The race for the Montana Senate seat will be an intense one, however, as control of the chamber will be very much at stake in 2014. The Democrat Caucus maintains a 55-45 majority in the Senate, but Baucus is the sixth veteran Democrat to announce he’s retiring in 2014.

Polls in Montana showed Baucus trailing likely Republican challengers. By contrast, Schweitzer has been running ahead of one and even with another. If he runs, he’ll bring to the race the populist approach that was on display at the 2012 Democratic National Convention. In Charlotte, he drew wild cheers for a speech that ripped Republican policies with the line: “In Montana, that dog don’t hunt.”

As Tom Tomorrow says, the Senate owns a special place in the failure that was last week.