WASHINGTON – Democratic U.S. Rep. Rick Nolan's biggest challenge in his re-election fight isn't Republican rival Stewart Mills so much as GOP presidential nominee Donald Trump.

Nolan's northern Minnesota congressional district is a hotbed of Trump support, even among some Democrats. Stung by the loss of blue-collar jobs in recent years, many on Minnesota's Iron Range welcome Trump's searing criticism of trade agreements and environmental regulations, and his pledge to help those who have fallen behind in the tumultuous global economy.

"When you've got a guy who is nationally talking about trade and wanting to help the miners, some of them believe him," said St. Louis County Commissioner Tom Rukavina, a DFLer who supports Nolan.

But Rukavina said he understands Iron Rangers' apprehension about Democrats. He says delays from DFL Gov. Mark Dayton's administration on proposed copper and nickel mining has hurt the party's popularity Up North. "People are frustrated, what do they [the Democrats] expect?"

Nolan faces stiff headwinds, even in the district's Democratic strongholds. And Democratic presidential nominee Hillary Clinton is not much help. Former Democratic hopeful Bernie Sanders trounced Clinton 65 percent to 35 percent in the district's precinct caucuses.

Leaders from both parties consider Nolan to be one of the most vulnerable House Democrats in the country — a dramatic swing for a congressional district that for decades was a lock for Democrats.

"I've been here all my life. … People know me," said Nolan in a phone interview between campaign events. "I'm not taking anything for granted, though. It's going to be a close race."

Republican rival Stewart Mills has worked to paint Nolan as ineffective and out of touch. He called Nolan's efforts to help miners too little, too late.

"There is a lot of frustration with congressman Nolan," Mills said.

In recent days, Nolan has made a surprising shift in tack and message. From initially endorsing Sanders and railing against the political system, Nolan has recently begun praising President Obama for helping the district regain some mining jobs. Nolan is also touting his work as a D.C. insider — including convincing Obama's chief of staff and native Minnesotan Denis McDonough to visit the Range last year and chat up laid-off miners — as key to bringing some relief to the economically battered area.

This week, Nolan wrote a thank-you letter to President Obama for imposing high steel tariffs that led to 1,000 iron ore miners returning to work.

"As our workers return to their jobs, the Iron Range is on the road to economic recovery," Nolan wrote in the letter to the White House. "Iron ore and steel prices are up, the glut of foreign steel on the U.S. market is disappearing."

The letter was something of a calculated gamble for Nolan, claiming victory for voters feeling better when they may not indeed feel better.

Eveleth Mayor Robert Vlaisavljevich is an example of how hard of a sell that will be. The lifelong DFLer penned a letter to the editor of the local newspaper endorsing Mills and Trump, blasting what he sees as the liberal "phonies" taking over the party.

"It's time that the real Democrats come out to show what we value most," he wrote. "If this election falls to the liberal radicals, we could very well see the last generation of miners in Minnesota."

An heir to the Mills Fleet Farm fortune who is self-funding a share of his campaign, Mills mostly embraces Trump. He likes to cite a memorable conversation with a voter in his district who supports Trump, saying he favored him "cuz he's going to shake up Washington, D.C., like a jar of nickels."

Mills' embrace of Trump comes as other Republican congressional candidates in Minnesota and around the country have distanced themselves from the GOP nominee.

Mills said he disagreed with some of Trump's rhetoric, but compared it to being married.

"I don't agree with everything my wife says," he said. "Donald Trump is a beneficiary of the fact that Hillary Clinton is not to be trusted. It's time for a change. People want a bold new vision. … People don't want business as usual, they want someone with a bold agenda."

Minnesota's DFL Chair Ken Martin said he expects Nolan to overcome the anti-establishment tide — but that it may be the state's closest race in November. Over the last two presidential cycles, the district has grown more conservative: U.S. Sen. John McCain lost to Obama by almost nine points in 2008. Four years later, Obama won the district again, but by six points.

"I'm not cocky about this race," Martin said. "People are frustrated. ... The Iron Range and northeast Minnesota's economy hasn't improved like other parts of the state, and traditional Democratic votes have been bleeding off because of issues like that."

Trump's state director, Mike Lukach, said he is encouraged by momentum in the Eighth Congressional District — Trump placed second in March's precinct caucuses, just behind Ted Cruz. He touted Trump's stances against trade, immigration and for VA reform as reasons he is popular in northern Minnesota.

"Voters in northern Minnesota understand that Hillary Clinton represents a third Obama term, while the Trump-Pence campaign of tougher law enforcement, stopping illegal immigration and bringing back jobs is resonating strongly across the Eighth," he said in a statement. "Voters are tired of the same old Washington corruption and backroom deals."

Cindy Rugeley, a political scientist at the University of Minnesota Duluth, said Trump is not going to hurt Mills like he may other state Republicans.

"I haven't seen the enthusiasm for Hillary that you would expect in a Democratic district," Rugeley said. "The Trump message about trade will make a difference, and it is the same message Mills has about Nolan, which is that he hasn't been strong enough on helping miners."

Allison Sherry • 202-662-7433