WASHINGTON - In the clubby atmosphere of the U.S. Senate, with its premium on going along to get along, Mark Dayton sometimes stood out for going it alone. Not always with happy results.

Now, locked in a three-way battle to be Minnesota's next governor, a long record in public office that spans U.S. senator, state auditor and state economic development commissioner provides much for supporters and foes to say about Dayton.

The two seminal events of his six years in Washington both involved acts that could alternately be cast as profiles in courage or weakness, depending on the partisan spin.

The vote that largely defined Dayton's Senate career came in the run-up to the U.S.-led invasion of Iraq. Dayton and fellow Minnesota Democrat Paul Wellstone were among only 23 senators to oppose President George W. Bush's war powers resolution.

Dayton counts it as one of his proudest moments -- a tough vote that came after a sleepless night of deliberation.

The other event wasn't a vote, but a staffing decision he made two years later while at home in Minneapolis during a congressional recess.

In a move that rankled much of official Washington, Dayton became the sole member of Congress to heed classified warnings of a potential pre-election terror attack in the city. He acted decisively, temporarily closing his D.C. office to spare his young staffers and any visitors unnecessary exposure to danger. The move garnered nationwide press attention -- much of it unflattering -- and has been raised in opposition campaign ads in the current governor's race.

It was easily the biggest rumpus in a long public career that has spanned 35 years.

Fresh out of Yale University, Dayton started his work life as a teacher in New York City, followed by a stint as a social worker in Boston.

In the mid-1970s he became a legislative assistant to then-U.S. Sen. Walter Mondale -- a job that gave him a lifelong taste for political life. He started close to the top, making a bid for U.S. Senate in 1982. He came close, but lost by 6 percentage points to Republican David Durenberger.

Dayton claimed a clear victory in 1990, when he handily won the race for state auditor.

Dollar a year

As auditor, Dayton established a ferocious reputation for attacking government waste and guarding taxpayer money. He did it in his own style, forgoing the auditor's salary in favor of $1 a year.

In 1995, on his last day as auditor, Dayton returned $1 million from his office to the state treasury. The gesture, he said, "out-Republicans the Republicans." During his four years, Dayton openly took on former DFL Gov. Rudy Perpich, calling him "greedy" for seeking a higher public pension. In what would become a refrain of Republicans, he also criticized local governments for using tax money to lobby the state.

Dayton was among the first to warn that public school pension funds in Minneapolis, St. Paul and Duluth weren't getting adequate investment returns -- an issue that has come back to haunt taxpayers and retirees alike.

One of his biggest crusades involved audits of the Minneapolis Community Development Agency, probes that highlighted loose financial controls and described an agency governed more by local pork-barrel considerations than by a citywide strategic plan.

When Dayton announced in early 1994 that he would not seek a second term as auditor, he explained that he wanted to deepen his spiritual life "and grow as a human being," but had no specific plans after his term ended.

"I'm not disappearing," he said at a State Capitol news conference. "I intend to seek public office in the future."

Senate frustrations

In 2000, Dayton finally achieved the prize that had eluded him for so long -- a U.S. Senate seat.

But when he arrived, it was as part of the minority party, with Republicans controlling the presidency and the Senate.

He co-sponsored 22 bills that were enacted into law over his six years, but he failed to pass a single bill he introduced.

He was not alone. Nevada Sen. Harry Reid, a Democratic whip and then leader, passed only three bills in that time. Freshman Sen. Barack Obama, of Illinois, passed two.

As a liberal Democrat, Dayton still found some common ground with Republicans. He sided with President Bush on Medicare coverage of prescription drugs -- a top priority for both. Dayton, who drove a flex-fuel Ford Explorer around D.C., joined forces with Republicans on an energy bill with generous ethanol subsidies that drew sharp criticism from some of his best friends in the environmental movement.

He succeeded in resurrecting one of his bills -- to help displaced taconite workers on the Iron Range -- as part of the Trade Act of 2002.

Eventually, Dayton would find a measure of vindication on the Iraq war vote, the marquee issue of the time, as public sentiment toward the war cooled. But the fallout from closing his office persisted and played a role in his decision not to seek a second term in 2006.

A failing grade

Leaving Washington at the end of one term, he gave the entire Senate -- himself included -- an "F." Time magazine listed him among the "worst senators," terming him a "blunderer."

Much of the critique stemmed from his office closure, his complaints about seniority and an ill-fated proposal for a Cabinet-level Department of Peace and Nonviolence in 2005 that went nowhere. Bill Walsh, then executive director of the Minnesota Republican Party, called the measure "naïve" -- a word that encapsulated much of the Republican critique of Dayton's Senate tenure.

Iowa Sen. Tom Harkin, a Democrat who worked with him on the Agriculture Committee, credits him with "giving agriculture a foothold in the renewable energy industry."

Dayton's popularity with seniors had helped him get elected to the Senate in 2000, just as it helped propel him to victory in this year's DFL gubernatorial primary.

He devoted his Senate salary to help pay for bus trips for seniors to go to Canada for cheaper prescription drugs. Still, he never realized one of the greatest ambitions of his health care agenda: a plan to allow the federal government to negotiate lower Medicare drug prices with drug companies. Just as Bush had done when Dayton was in the Senate, Obama left it out of his health care overhaul.

'Proactive'

While Dayton sometimes complained about political gamesmanship in the Senate and its incessant demand for political fundraising, by his final year in office he had become a more adept player.

In late 2006 he was criticized back home for placing a procedural block on an AIDS funding bill that would send nearly $3.8 million to Minnesota. Dayton was actually stalling to buy time for other senators -- including Hillary Clinton -- to head off funding cuts for their states. The bill later passed.

Hours before he was to end his term on Jan. 3, 2007, Dayton speculated that he would be a better fit in a more "proactive" job.

The job he mentioned? Governor in 2010.

Pat Doyle • 651-222-1210 Kevin Diaz is a correspondent in the Star Tribune Washington Bureau.