When Rep. Tina Liebling began knocking on doors during her first race for the Legislature in 2002, some Rochester voters told her they were — “shhh” — Democrats.

“They would say, ‘I’m a DFLer too but don’t tell anyone,’ ” said Liebling, who in 2004 became the first Democrat in the era of partisan legislative elections to win a seat from Rochester.

Now, the DFL is making an aggressive play for votes in fast-growing, rapidly diversifying Rochester — county seat of Olmsted County — which anchors southern Minnesota and is home to Mayo Clinic, the state’s largest private employer.

But there’s another side of the story. In northeastern Minnesota, a union and DFL stronghold going back nearly a century, Democrats’ firm grip is slipping. An aging population there is comfortable with the cultural conservatism and aggressive trade posture of President Donald Trump — especially when it comes to helping the local steel industry.

There’s also a wariness of a Democratic Party whose center of gravity is being pulled ideologically to the left and geographically south toward the more urban sensibilities of the Twin Cities and other growing parts of the state, like Rochester.

“Elizabeth Warren comes to town and right away makes an anti-mining statement,” said state Sen. Tom Bakk, DFL-Cook, referring to the presidential candidate’s recent statement opposing copper-nickel mining in Superior National Forest. “When those things are critical to the health of your community, and you see high-ranking officials against them, it makes it hard to support the party if that’s the perception.”

The contrast between north and south neatly reflects the Democrats’ identity crisis across the country. People of color, single women and suburbanites who detest Trump make up the party’s emerging coalition, but they cannot win without at least some support from working-class whites who in another era formed the Democratic base.

Ruy Teixeira, a Democratic pollster who predicted the party’s path in the 2002 book, “The Emerging Democratic Majority,” said Democrats would be foolish to follow one path at the expense of the other.

“The case I try to make is they need to do both. You might do better in growing cosmopolitan areas, but you can still lose. It happened in 2016, and it could happen again in 2020,” he said.

The stakes for both parties and both regions are enormous: After the 2020 election and census, the Legislature will redraw both congressional and legislative maps, setting the stage for the next decade of Minnesota politics. Minnesota is on pace to lose a congressional district — likely to a faster-growing state in the South, like Texas.

More immediately, the DFL sees opportunities to target state Senate districts next year that could determine control of state government going into redistricting. Democrats also would like to pick off two newly elected GOP congressmen: Pete Stauber in northern Minnesota’s Eighth Congressional District and Jim Hagedorn in southern Minnesota’s First Congressional District.

But the majority of the national party’s fire has been focused on Hagedorn, not Stauber.

DFL operative Kendal Killian, a Duluth native who ran former Rep. Rick Nolan’s 2014 race in the Eighth, said the First currently offers more fertile ground.

Republicans say the DFL has left behind voters like those in the Eighth. “The Democratic Party has shifted from the days of Rudy Perpich,” said GOP operative Gina Countryman, referring to the Iron Range’s favorite son and the state’s governor in the 1970s and again in the 1980s. “It wasn’t uncommon to find a Democrat who was pro-life and pro-gun rights. The change has driven those people away,” Countryman said.

DFL Chairman Ken Martin concedes the party’s 2016 problems in northeastern Minnesota, dragged down by Hillary Clinton’s lackluster candidacy. But he and his staff cite 2018 voting data showing the DFL retaining strength in St. Louis County around Duluth, as well as in smaller counties of northeastern Minnesota.

For her part, Countryman acknowledges the challenges the GOP faces in areas like Olmsted County that are both growing and changing. She said Republicans need to offer a fresh message — especially with college-educated voters who were once staunch Republicans and are now flooding to Rochester to work at Mayo and other businesses. “It’s a challenge for parties to be relevant to what voters are saying today and not what they were saying in the past,” she said.

At first glance, the northern Eighth Congressional District and the southern First District seem similar. Both are geographically large and rural compared to most districts where the DFL remains competitive. Trump won both by 15 percentage points, and Republicans flipped both congressional seats in 2018, sending Stauber and Hagedorn to Congress.

But a closer examination reveals small differences that are nevertheless significant in close elections and provide fodder for party strategists who are looking south. Nearly 1 in 7 residents of the southern First District are nonwhite, while fewer than 1 in 10 in the northern Eighth identify that way. The First has more women, more black people and more young voters — all reliable DFL constituencies. And the First, especially Olmsted County, is home to more of another emerging DFL constituency: people with college and graduate degrees.

“It’s obvious. It’s burgeoning communities of color and Mayo,” said Killian about the party’s shifting focus.

Longtime DFL operative Jeff Blodgett said that in statewide races, when it comes to providing votes to supplement the Twin Cities metro, “The First is poised to replace the Eighth in terms of the assistance it provides to the DFL.”

Election results in recent years reflect the subtle differences. Dan Feehan lost narrowly to Hagedorn by a little more than 1,300 votes last year in southern Minnesota, whereas Stauber won a commanding victory in northeast Minnesota by more than 17,000 votes. Despite his loss, Feehan showed the party’s growing momentum in Olmsted County, where he improved on the performance of then-Rep. Tim Walz’s 2016 vote percentage there.

Feehan is expected to run again in what will be one of the most heavily targeted races in the country. By contrast, the DFL doesn’t have an obvious candidate in the Eighth, and DFL strategists acknowledge that Stauber will be tough to beat.

Walz, who represented southern Minnesota in Congress for 12 years, showed the decreasing importance of the Eighth for the DFL in last year’s governor’s race. His Republican opponent, Jeff Johnson, won the Eighth by more than 5,000 votes, while Walz won his home First District by nearly 7,000 votes. These results reversed the 2014 results, when former DFL Gov. Mark Dayton won the Eighth but lost the First.

Bakk hopes that Walz will be the DFL’s stalwart in both regions. Democrats believe that Walz, as a former soldier, teacher and football coach, can connect culturally with the more rural, aging voters in northeast Minnesota.

But Walz may represent a more ominous trend for Bakk and his fellow northeastern Minnesotans. Olmsted is the major population center of the First District, and it has grown by more than one-fourth since 2000. St. Louis County, on the other hand, has nearly the same population it did at the turn of the century.

In other words, the first governor from southern Minnesota in the postwar era is also a reflection of a bigger trend: Power and influence in Minnesota are moving south.

Staff data visuals editor C.J. Sinner contributed to this report.