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Leaning against a light blue convertible and waiting to take his place in the annual homecoming parade in Marshall, Minn., Collin Peterson recounted a recent 3 a.m. phone call from House Speaker Nancy Pelosi.

"I told her, 'This whole campaign is about you. They're saying I've become a liberal and I'm doing whatever you tell me,' which is ridiculous," he vented through his face mask. On the call, he proposed to Pelosi a solution: "What we need to do is have you come up here and tell them I'm a completely soulless S.O.B."

Minnesota's Seventh District congressman for three decades, Peterson has developed close working relationships with Pelosi and other House leaders over his long tenure, forming allies in both parties that helped him rise to chair the powerful House Agriculture Committee. But at 76, his increasingly tenuous ties to urban Democrats in his party have been a weight around his neck in his rural, conservative Minnesota district. It's a weight that gets heavier each election cycle.

Four years ago, Donald Trump won Peterson's Seventh District by more than 30 percentage points over Hillary Clinton. Peterson, meanwhile, beat a little-known Republican challenger by 5% of the vote. This year, Republicans see an opening with Trump back on the ballot. They've recruited former lieutenant governor and state senator Michelle Fisch­bach and are investing millions in what they see as one of their best chances to flip a blue district red this fall.

It's a new twist on an old problem for Peterson, who has held on to his seat through multiple Republican waves while other conservative Democratic allies were defeated or left an increasingly polarized Congress. This cycle, he's more isolated than ever.

He was among 45 Democrats who voted against the 2010 version of the Affordable Care Act that became law. Now, he's one of three left. He was one of two Democrats who voted against impeaching Trump late last year. The other member, Rep. Jeff Van Drew of New Jersey, is now a Republican. He opposes abortion and is the lone Democrat in Congress with an A-rating from the NRA. "If I hear the words 'common sense gun legislation one more time,' " he said last year, "I'll throw up." Many of those left in the Blue Dog caucus might have been considered insufficiently conservative when he originally co-founded the group.

"The Blue Dogs were for conservative Democrats," said Peterson. "I'm the only conservative Democrat left, basically."

His conservative positions have, at times, earned him the ire and befuddlement of more progressive Minnesota Democrats in the metro area, who couldn't understand why a member of their party voted against impeaching Trump. He's tried to distance himself from members of Minnesota's delegation such as Fifth District Rep. Ilhan Omar, a darling of the progressive left. In a recent video filmed on Capitol Hill, a Republican campaign operative followed Peterson and asked why he defends Omar. Peterson replied that he doesn't defend her, with a blunt follow-up: "She doesn't belong in our party."

But Peterson's conservative instincts have been a key part of his political survival all these years in a rural district that most Democrats concede would have been lost long ago without him. His campaign ads easily could be mistaken for a Republican's this cycle, touting his vote against impeachment, support from law enforcement and opposition to environmentalists trying to block the Line 3 pipeline replacement project in northern Minnesota. A supporter recently called one of his staffers in a panic because they saw Peterson's signs next to Trump signs along Hwy. 212. "How do you think he gets elected?" his staffer replied.

"He calibrates his relationships with the Democratic Party very carefully," said David Sturrock, a political-science professor at Southwest Minnesota State University in Marshall and Republican who ran against Peterson in 2004. "He doesn't allow himself to get dragged into things that are not part of his portfolio."

Peterson's portfolio is farming, where he has made his biggest mark in Congress. At home, his politics and his campaign style defy modern day conventions. He doesn't announce whether he plans to run again until the last possible moment, and he often raises less money than his opponents. An accountant by profession, he learned how to fly a single-engine airplane to get around his district, which stretches roughly 35,000 square miles across almost the entire western border of the state.

When Peterson announced his first run for a seat in the state Senate in 1976, he marched into a newspaper office without knowing who his opponent would be. Still, Peterson won that year after spending the summer going from farm to farm to make his case. Roger Moe, the former Senate DFL leader who recruited him to run, said Peterson has "probably never written a speech in his life. He just talks to people."

It took four tries for him to get to Congress in 1990, and still today, Peterson relies on support from agriculture to stay there. He backed Trump's trade deal and was a key player in shepherding multiple farm bills through Congress. He's earned the nickname "the godfather of sugar" for his work with the sugar beet industry. The district is the largest sugar producer in the nation, competing with sugar cane operators in the South. In a sure sign of his importance, the sugar industry has created a super PAC with the sole purpose of re-electing Peterson, raising more than $1 million to spend in a race that's seen more than $9 million in outside spending so far.

"He understands ag better than anyone in Congress today, and I consider him a friend. He calls me up and asks about my horse sometimes," said Curtis Knutson, a fifth-generation farmer in Fisher, Minn., who served more than a decade on the board of American Crystal Sugar. Knutson votes red in most races but blue in the Seventh District race, and he sees Peterson's relationship with Pelosi as an asset in a year where he expects the U.S. House to remain in Democratic control.

It's agriculture that's kept Peterson from retiring from Congress, despite his growing frustrations with his party and polarization in Washington. He'd like to work on another farm bill, and he said he's worried about the clout his district — particularly the farmers — will lose in Congress when he's gone.

Whatever happens, Peterson doesn't plan to change parties after a long career in state and federal politics that he's built on a go-your-own way approach. "I'm going to survive on my own, and if I don't survive, well, I'm not going to change," he said. "I haven't changed all this time."

Briana Bierschbach • 651-925-5042

Twitter: @bbierschbach