WASHINGTON – Democratic U.S. Rep. Rick Nolan is leaving Congress in a few days with a gnawing sense of frustration over things left undone.

"One of the things I wish I could have done a better job of accomplishing is getting people to understand the relationship between the process and money in politics," Nolan said.

The partial federal government shutdown gripping the nation is serving as the latest reminder of the partisan gridlock that he has railed against for decades during his two stints in Congress.

With his retirement days away, Nolan no longer even occupies his own office, which has been turned over to a new member. "Congress is dysfunctional," he said.

So much has changed in Washington and in his own congressional district, which encompasses a giant swath of northeastern Minnesota and the heart of the state's embattled mining industry. Nolan's first election in 1973 came at a time when northern Minnesota had a stronger Democratic lean. But over the years, Republicans made deep inroads as the local economy languished and union influence waned.

Nolan's replacement is Republican Pete Stauber, a strongly pro-mining candidate who capitalized on President Donald Trump's popularity in the district. The president won the district by 15 points, promising to bring back mining and manufacturing jobs.

Nolan chose a tricky political path in recent years, framing himself as a progressive who supports mining expansion. His work to speed up a necessary land swap for the proposed PolyMet copper-nickel mine drew intense criticism from some traditional Democratic allies, who say the project needs more review.

"I think people can agree or disagree about whether copper-nickel mining near Lake Superior is a good thing, but I don't think Minnesotans should disagree about whether due process is a good thing," said Paula Maccabee, an attorney for Water Legacy, an organization that is one of the plaintiffs suing over the land swap.

As a wave of younger and more diverse Democrats prepare to take control of the House, Nolan's departure leaves just one of the "Watergate babies" left in Congress: Sen. Patrick Leahy of Vermont.

They were part of the historic wave of Democrats that swept into office in 1974 after the Watergate scandal led to President Richard Nixon's resignation and calls to overhaul how government operates.

Nolan sees similarities with today. "Back then, there was no great love for Democrats, but there was a bitter disgust with what was happening in the Republican Party and Richard Nixon. I just told my friends that people were going to get into the booth [in 2018] and they may not be wildly enthusiastic about Democrats, but they've had it with the Republicans."

The problems of Congress go far beyond any single political party, he said. Nolan left office in 1981 and pursued a career in domestic and international business.

When he returned to Congress in 2013, he was surprised by the grueling demands to raise money and the increasingly secretive dealings among a handful of legislative leaders. He found himself traveling eight hours twice a week just to go back and forth from Washington, which ate up time he could be spending on issues or crafting legislative proposals.

Some of Nolan's biggest frustrations are with the changing nature of campaigns, which are increasingly fueled by money from outside groups the candidates themselves can't control. In his own district, outside groups spent $9.6 million this election; most of it was from organizations paying for negative ads against Democrat Joe Radinovich, who lost to Stauber.

Nolan has advocated for ending unlimited election spending by corporations and labor unions under the Supreme Court's Citizens United ruling in 2010.

All the spending on negative ads "creates this notion that all political people are awful … it erodes democracy," said Nolan.

Nolan said he's encouraged by the diverse new wave of more liberal-leaning Democrats coming to Congress. But high-profile efforts to elevate these freshman members to influential committee spots are "more window-dressing than anything else," said Nolan, a member of the Congressional Progressive Caucus.

These coveted committee assignments don't reduce the nearly constant demand to raise money or give them more say when deals are being cut, Nolan said.

They "do offer new members vehicles and opportunities to demonstrate what kind of leadership qualities they have, but it doesn't solve the fundamental problem of a handful of people making all the decisions around this place."

Nolan has repeatedly said he is retiring from politics to spend more time with his family. His daughter was diagnosed with advanced lung cancer, and that day, he wished he was with her at Mayo Clinic.

He has also faced health struggles of his own: Nolan had a heart attack about six weeks ago, which followed one in March, the month after he announced he was leaving Congress. It was also just before his stint as running mate of unsuccessful gubernatorial candidate Lori Swanson.

But pressed further, Nolan acknowledged that the breakdown of the political system — and its inability to address income inequality and other major issues — had influenced the decision.

"If I thought that Congress was geared up to tackle these big issues, you couldn't get me out of here with a team of horses," said Nolan.

Nolan's frustration with Washington surfaced soon after returning to Congress in 2013. At the time, he said he was surprised by the light workload. "We're not working four or five days a week, like everybody else does in America," Nolan said at the time.

Today, he sounds more skeptical or even jaded about Washington. He likes the energy of the new Democrats coming aboard, and "there's a number of bright elders that are going to be here to channel and guide that. Unfortunately not much progress is going to be made, but there will be the building of a case for it."