PHILADELPHIA - Gov. Mark Dayton attended his first Democratic National Convention 40 years ago in New York City, serving as a junior aide to Sen. Walter Mondale and volunteering for the convention effort, working the floor for information.

When Jimmy Carter picked Mondale to be his vice presidential nominee during the convention, Dayton did the advance work for Mondale's acceptance speech, maneuvering him through the bowels of Madison Square Garden with a ravenous press in pursuit.

Four decades later, Dayton was on stage to address the convention in support of his friend and former Senate seatmate Hillary Clinton, who accepted the nomination Thursday.

"This one is very meaningful because I have known her," said Dayton, who called Clinton the hardest working public official he has ever seen.

In between these high moments, a lifetime in politics has yielded its share of crushing disappointments, including both policy and political defeats.

Dayton drew on that experience this week to address supporters of the second place finisher on the Democratic side.

"I want to talk to the Bernie Sanders delegates," Dayton told a breakfast meeting of the Minnesota delegation, growing emotional as he evoked campaigns past.

"One of the reasons [Sanders] was so successful is that he sounds a lot like Paul Wellstone, and that's a high compliment," Dayton said of his late friend, the former U.S. senator who continues to be an icon in progressive Minnesota politics.

"I understand what it feels like. I remember when Paul died, the sense of loss, the sense of nihilism, you know — what matters? [Sen.] Strom Thurmond gets to live to 100, and Paul Wellstone doesn't make it to 60? Why God? What's the point?"

Dayton said later in an interview with the Star Tribune that before he spoke, he had been sitting with a young Sanders delegate, who related she was so upset that she had to leave Tuesday's roll call vote when Clinton was finally nominated.

"I could tell she was deeply affected, and I thought, 'I've known that feeling.' And Paul's tragedy came to mind," he said.

"The death of a campaign is a very profound thing. Especially when you're young," he said.

After Wellstone's death, Dayton's Senate term was — by his own admission — a failure, having once given himself an F while speaking to a high school group.

But he picked himself up after the disappointment.

"I knew Paul would want us to carry on. I could hear him pressing all of us to carry on what he had illuminated for us," he said. "The choice was nihilism or activism. I chose activism, as I hope Sanders people will choose."

Dayton left the Senate after just one term in 2006 but worked hard for Clinton in her first presidential run and began plotting his path out of the wilderness.

"Perseverance is a prerequisite for success in political life," said Dayton, a department store heir.

Former U.S. Sen. Ted Kennedy gave him that advice during a moonlight walk along the beach at the Kennedy compound in the early 1990s, Dayton relayed. It's the kind of story only Dayton could tell, his ties to the country's moneyed political elite rare among Minnesotans.

Dayton said he has always remembered Kennedy's guidance.

Ken Martin, chair of the DFL, said Dayton's willingness to take political hits — including losses — and get back up and trudge on has made him a better governor.

Martin recalled the state government shutdown in 2011, when the DFL and its partners set up phone banks and were pounding Republicans who controlled the Legislature, only to have Dayton call off the effort and agree to GOP terms, much to the chagrin of party operatives.

"The long extended shutdown was hurting the state of Minnesota. And the governor said, 'It has to end. This isn't about scoring political points,' " Martin recalled.

Martin, who became head of the party at Dayton's urging, said he saw something in Dayton: "I left that meeting with real increased respect for Gov. Dayton. I believed we had a man who was guided by principal and standing up for what he thought was right and not what was politically expedient."

With this convention finished — most likely his last in elective office — Dayton again returns to a hothouse political environment. Many of his DFL allies, eyeing a fiercely competitive November election for control of the Legislature, want him to walk away from negotiations with GOP House Speaker Kurt Daudt over a special session to give tax breaks and spend hundreds of millions of dollars on public works projects.

Some DFLers are baffled Dayton would give the speaker a political victory just months before the election in which Daudt is desperately trying to hold on to his slim majority.

One thing is certain: With four decades of politics under his belt — taking him from the convention floor for a vice president to the stage for a presidential nominee — Dayton will trust his instincts.

J. Patrick Coolican • 651-925-5042