U.S. Rep. Rick Nolan said Friday that he will not run for re-election this year, an unexpected decision that elevates the stakes in what was already going to be an expensive, all-out battle between Democrats and Republicans for his northeastern Minnesota congressional seat.

“Now is the time for me to pass the baton to the next generation,” Nolan, a Democrat, said in a statement announcing his retirement.

Nolan, 74, won two tough re-election campaigns since first winning the seat in 2012. Nolan publicly entertained a run for governor last year, only to announce last summer that he would run again in the Eighth Congressional District — once a Democratic stronghold but increasingly competitive for Republicans.

On Friday, Nolan reversed course. In a one-page statement, he promised to “finish strong” as he served out the remaining months of his term.

“Despite the fact that our nation is being challenged by some rather troubling politics, let’s remember that our founders foresaw difficult times and gave us the tools to see them through,” Nolan said. “Our constitution is strong, our people are resilient, and the elections of 2018, 2020 and beyond provide continuing opportunities for progress, reform and necessary change.”

Nolan, who was not available for an interview, also cited a need to spend more time with family. Calling them patient and supportive of his political career, Nolan said that “it’s time for me to respond in kind.” He has spoken publicly about his adult daughter’s struggles after a stage 4 lung cancer diagnosis three years ago.

As he prepares to wind down his time in office, Nolan said that jobs are coming back to his district and wages are rising. The sprawling district includes the Iron Range, Duluth and the Arrowhead region, and also stretches south to exurban counties north of the Twin Cities.

Fellow Democrats in the Minnesota congressional delegation praised him Friday.

“With a twinkle in his eye and a big heart, he’s been a joy to work with … and by the way, he’s such a rabble rouser,” Sen. Amy Klobuchar tweeted.

Rep. Betty McCollum, occasionally at odds with Nolan over mining issues, called him “a tireless champion for Minnesota.”

Nolan previously served as a congressman from 1975 to 1981, when he cosponsored legislation protecting the Boundary Waters. He’s spoken about how Congress has changed substantially since his first stint, and not for the better.

“It seems like I took a nap and I came back and I say, ‘Wow, what happened to this place? What’s happened to democracy?’ I mean, the Congress of the United States has hardly become a democratic institution anymore,” Nolan told “60 Minutes” in 2016, criticizing a system that pressures lawmakers to spend much of their time dialing for campaign donations.

Nolan’s recent elections have been among the most competitive and expensive in the nation, as the district has shifted toward Republicans. President Donald Trump carried the Eighth by 16 points in 2016, and Nolan defeated GOP challenger Stewart Mills by only 2,009 votes that year.

A spokesperson for the National Republican Campaign Committee (NRCC) said Friday that the district is a top priority, and the Minnesota GOP called it one of the biggest pickup opportunities for national Republicans. The leading Republican candidate so far this year has been Pete Stauber, a St. Louis County Board member and retired Duluth police officer.

“Minnesota’s Eighth District was already a top pickup opportunity in the country for national Republicans, and today’s news [puts] Stauber in an even stronger position,” read a statement from the state GOP.

Last fall, Mills said he wouldn’t run against Nolan for a third time, and criticized the NRCC for its failure to adequately support his campaign. The GOP left us “flat footed and unable to mount a commensurate campaign,” Mills wrote on Facebook. But after Nolan’s announcement Friday, Mills edged back toward a possible run.

“I have received numerous calls, emails and messages. I am very seriously considering another run for U.S. Congress to represent Minnesota’s 8th District,” Mills tweeted.

The Legislature’s two top-ranking Republicans, House Speaker Kurt Daudt of rural Isanti County and Senate Majority Leader Paul Gazelka of Nisswa, both live in the Eighth District; both could face requests from party leaders to consider the race.

On the Democratic side, Leah Phifer announced last year that she would challenge Nolan for the party endorsement. The former FBI counterterrorism analyst criticized him for being too friendly to mining interests.

Nolan had actively opposed the Obama administration’s two-year moratorium on mining near the Boundary Waters Canoe Area Wilderness, along with the federal government’s move against renewing mineral leases for Twin Metals, which is proposing a copper-nickel mine southeast of Ely.

Phifer said that she looked forward to furthering Nolan’s progressive legacy on single-payer health care and campaign finance reform, and to bridging the local DFL’s divisions between mining and job concerns, Bernie Sanders and Hillary Clinton supporters, and different geographic areas.

The Democratic Congressional Campaign Committee expressed confidence in holding the seat, with the group’s chairman, U.S. Rep. Ben Ray Lujan, D-N.M., calling it “a Democratic seat, and that certainly will not change in 2018.”

Phifer is unlikely to clear the field, with a number of current and former elected DFL officials from Duluth, the Iron Range and other parts of northeastern Minnesota as possible candidates. Joe Radinovich, a DFLer from Nolan’s hometown of Crosby, plans to spend the weekend talking to his family about running.

“It’s a pretty unexpected set of circumstances,” said Radinovich, a former state representative who served as Nolan’s 2016 campaign manager and is currently Minneapolis Mayor Jacob Frey’s chief of staff.

Two other potential Democratic candidates are state Rep. Jason Metsa of Virginia, who confirmed his interest Friday in a news release; and Jeff Anderson of Duluth, a Nolan aide and former member of the Duluth City Council.

Don Ness, a DFLer and former Duluth mayor, said the district has fundamentally changed over the past 20 years. Gone are the days when longtime Democratic Rep. Jim Oberstar won his races handily; he was Minnesota’s longest-serving U.S. House member, losing the seat to a Republican in 2010 and dying in 2014.

And with Nolan’s announcement nine months before the election, “there’s just not the time you would otherwise like to have for thoughtful consideration on who the party’s candidate is going to be,” said Ness, adding that he is not interested in running.

State DFL Chairman Ken Martin said that Nolan’s departure — which surprised him — adds another wrinkle in an already politically challenging year. Minnesota will have two U.S. Senate races and an open gubernatorial race. U.S. Rep. Tim Walz, also a Democrat, is leaving an open seat in southern Minnesota as he makes a play for governor. That leaves the DFL without incumbents in two congressional districts that Trump carried last year.

Meanwhile, Republican Reps. Jason Lewis and Erik Paulsen are expected to have competitive re-election bids as they try to hold suburban districts.

Martin predicted that the race to succeed Nolan will be the most competitive and expensive in the country.

“There’s going to be a lot of resources flowing in from both sides,” Martin said. “It’s just a district that Republicans feel is ripe for the picking and that Democrats feel they’re going to absolutely have to defend to win the majority back.”