DURHAM — Democratic voters seeking to take back a U.S. Senate seat in closely divided North Carolina must choose whether liberal populism or centrist pragmatism is best suited to unseat Republican incumbent Thom Tillis, a devotee of President Donald Trump.

Next month’s Democratic Senate primary has some parallels to the presidential race in that voters are trying to decide which candidate — and which philosophy — has the best shot at defeating the Republican incumbent. But it's not neatly delineated.

The stakes are high in North Carolina, a presidential swing state that Trump won in 2016. Tillis is among a handful of Republican incumbents whom Democrats are targeting to take back control of the chamber.

Underscoring the seat's importance, a mysterious PAC funded by a group with ties to Republican Senate Majority Leader Mitch McConnell has spent around $3 million in the Democratic primary to help a Senate candidate well behind in fundraising — an effort to create a taxing Democratic battle that could help Tillis stay in office.

The leading candidates are ex-state legislator Cal Cunningham, an Iraq war veteran who ran unsuccessfully for U.S. Senate 10 years ago, and current state Sen. Erica Smith.

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Democrat Ella Nelson, 65, who attended a Black History Month parade in Durham where Cunningham and Smith appeared, said she was undecided on a choice but focused on finding someone who can beat Tillis.

It’s about “replacing those that are not working for the people,” Nelson said.

Cunningham has the endorsement of the Democratic Senatorial Campaign Committee. The committee, two pro-Cunningham super PACs and Cunningham's campaign have spent over $10 million for the primary, campaign finance reports show.

Cunningham's campaign is “performing at a very high level, the level that the campaign needs to perform to unseat a Republican incumbent in a purple state and a battleground,” he said in a recent interview.

Smith, a former engineer turned K-12 teacher and pastor from northeastern North Carolina, criticizes Cunningham as “the establishment’s pick” and says party leaders are stacking the deck against her as a black woman.

Both candidates describe themselves as progressive and say they will support whoever becomes the Democratic presidential nominee. But they are clearly in separate political lanes.

While Smith said she won't endorse a presidential candidate before the primary, her platform is aligned with those who embrace Bernie Sanders and Elizabeth Warren on policies such as Medicare for All and the Green New Deal.

Cunningham said he cast his absentee vote for moderate Pete Buttigieg, citing the candidate's focus on faith and their shared military service.

Cunningham supports some kind of public insurance option — but not Medicare for All — and is a proponent of wind and solar power to combat climate change. He opposes efforts to decriminalize border crossings.

In an interview, Smith described her platform as "job creation, being able to have a livable wage, sustaining our planet, providing health care for all.”

Smith, who had $128,000 cash in mid-February compared to $1.5 million for Cunningham, is building name recognition from an unlikely — and uncomfortable — source. The Faith and Power PAC, funded entirely so far from the Senate Leadership Fund, which is led by McConnell's former chief of staff, has spent $2.9 million on pro-Smith TV ads, mailers and phone banks and anti-Cunningham materials.

“Who's got the courage to vote for ‘Medicare for All’? Erica Smith. The No. 1 supporter of the Green New Deal? Erica Smith again,” a narrator of one of the ads says. Senate Leadership Fund President Steven Law embraced the narrative that it's meddling to weaken Cunningham, calling it "more successful than we could have imagined."

While Cunningham has the inside track to the nomination, this unusual pro-Smith effort could help her, according to Mac McCorkle, a Duke University instructor and former Democratic consultant. Three other Democrats are on the ballot.

“It still may put her above water, and it could be a competitive race,” McCorkle said, adding that Cunningham hasn't fully ceded the liberal mantle. “He talks about himself as a progressive, which I think that's smart.” Cunningham has run a counterattack ad against one Faith and Power PAC commercial.

Meanwhile, Tillis — heavily favored to win his own four-candidate primary — argues his eventual opponent will have an uncomfortable situation if Sanders wins the presidential nomination.

“If Erica Smith believes people in North Carolina, and if Cal Cunningham believes people in North Carolina want Bernie Sanders and his liberal, progressive policies in place, then they need to be informed about it,” Tillis said in a news release. Tillis became one of President Trump’s most dependable supporters against impeachment; Cunningham and Smith have blasted him for it.

With African Americans expected to cast 40% of primary ballots, Cunningham and Smith are aggressively courting black voters. Smith's endorsement by the influential Durham Committee on the Affairs of Black People allowed her to stand on the group’s float in this month's parade.

Smith supporter and state employee Phyllis Jones, 49, of Raleigh said she's excited a black woman is on the ballot.

“We lend a voice in areas where we have been silent in the past,” Jones said.

But race didn’t matter to 63-year-old Delmar Jones — unrelated to Phyllis Jones — saying he appreciated shaking hands with Cunningham and his views on impeachment: “He means business, and I like the message."