Take a spin through Rochester, Minnesota, and there are signs of construction everywhere: The city is in the midst of a $5.6 billion expansion with the Mayo Clinic at its center. There are new shops, new apartments and new houses.

With a population of 116,000, Rochester is by far the biggest city in Minnesota’s First Congressional District, a largely rural band across the state’s southern border.

And Minnesota’s third largest city is growing. Rochester has added nearly 40,000 people in the last 20 years.

All that expansion is changing the city in more ways than one: As it’s grown, Rochester’s political makeup has changed, from Republican-leaning to more Democratic. The city went for George W. Bush by nearly 4 percentage points in 2000, in less than a decade it favored Barack Obama and then Hillary Clinton.

But Rochester’s growth isn’t the only change that’s come to the First District in recent years: Republicans have increased their margins of victory in the district.

That means Rochester, bigger and bluer, stands out in a part of the state that’s otherwise trending redder and hasn’t, on the whole, seen a lot of population growth; underlying attributes that make the race between DFLer Dan Feehan and Republican Jim Hagedorn one of the most closely-watched in the country.

A true swing district

At turns, the First District has been Trump Country, Obama Country, Bush Country and Walz Country.

Look no further than Election Night 2016, when DFL Rep. Tim Walz won re-election by a thin margin on the same night Republican Donald Trump carried the district by 15 points.

It’s the same district that in 2012 voted for Obama by a 1.3-point margin.

Things have gone downhill for the DFL in southern Minnesota since then.

At the congressional level, Republicans have been competitive in recent races against incumbent Walz. And this year, with Walz out of the race to run for governor, Democrats worry the open seat is vulnerable, as Republicans eye it as one potential pickup in a year where political winds seem to favor Democrats.

The majority of  state legislative seats within the boundaries of the First District — nine of 11 Senate seats and 13 out of 20 House seats — are held by Republicans, and in recent elections, Walz’s margins of victory have also eroded.

“This is definitely a district to watch and definitely one of the most competitive and swingy in the country, especially when you take in to account this is an open seat and the Republican nominee has performed very competitively the first two times he ran and now is going against a (DFL) political newcomer,” said Eric Ostermeier, a research fellow at the Humphrey School of Public Affairs’ Center for the Study of Politics and Governance.

Campaigning everywhere

Save for Rochester and a handful of other cities over 20,000 people, most of Minnesota’s First District is made up of small towns and rich farmland, divided into neat squares for hundreds of miles by county highways.

It’s in these places that Republicans amass votes in CD1: In 2016, Trump won by piling up votes outside major population centers, the biggest of which are Rochester, with 116,000 people or about 17 percent of the district’s population, and Mankato, at 42,000, or about 6 percent of its population.

Hagedorn’s votes in his near-successful 2016 bid came from similar quarters, except that he didn’t win by a large enough margin outside the population centers to make up for Walz’s lead within them.

Now making his third run, Hagedorn has the advantage of better name recognition, probably much moreso than Feehan, Ostermeier said.

But it could be an uphill climb this particular year. Based on the national mood, Hagedorn shouldn’t count on more DFL-leaning counties with larger towns and cities lacking energy in November, Ostermeier said. He has to hope Republicans are energized the way they were in 2016, though both sides are likely to see lower turnout, since it’s a midterm and not a presidential election year.

Closing the gap in the cities could help Hagedorn, but it’s not like the CD1 cities are a slam-dunk for Democrats — not like in the Twin Cities.

“We aren’t talking some of the numbers you obviously see in places like Minneapolis or St. Paul, where you might be 75  to 25 or 80 to 20 or something like that. That isn’t what you have in Rochester,” said David FitzSimmons, Hagedorn’s campaign manager.

Hagedorn’s strategy is campaigning everywhere, FitzSimmons said.

“He’s a very active campaigner, he’s shown up in towns large and small, everything from Rochester to Eitzen and Caledonia and places like that that are very small towns,” he said. “We focus everywhere, everyplace is where we’re trying to be to make sure that everyone in the district feels like they’re an as important part of the district.”

Stockpiling in the cities

For Democrats, there is a small and potentially decisive advantage in stockpiling votes in more populous areas, but it’s not enough.

For his DFL opponents, FitzSimmons said Rochester and Olmsted County are a sizable share of district-wide votes, but “even if you win in the city of Rochester or even if you win the county of Olmsted, if your margin wasn’t that big, there really aren’t that many banked total votes that you have to work off the rest of the district.”

Still, the question of whether some of the big gains Republicans made in 2016 are permanent or more a function of an anomalous election remains unanswered.

Some are optimistic that the prevailing political winds, which have propelled Democrats to unlikely victories or increased their margins in other states, will help the DFL convert places that have strayed back.

“We’re seeing more activism in every county this time around, so I think that certainly will depend on some of those more populated communities like Mankato and Rochester, and college communities like Winona, but I think we’ll do a lot better in some of the more rural counties like Nobles and Watonwan,” said Lori Sellner, a longtime DFL activist in Southern Minnesota and member of the Democratic National Committee.

If parts of the district that have trended redder don’t bounce back to the DFL in November, it’ll spell trouble for Feehan, Ostermeier said.

“He has to hope it reverses course in several of these counties, I think, to have any sort of confidence that he’s going to be able to hold the seat for the DFL,” Ostermeier said.