Democratic 2nd District House candidate Kara Eastman speaks to supporters in Omaha, Neb.
Washington CNN  — 

A nonprofit executive who campaigned on offering “Medicare for all,” stunned the Democratic establishment and secured one of the activist left’s biggest wins yet Tuesday in a House primary in Nebraska.

Kara Eastman defeated the better-known former Rep. Brad Ashford, a “Blue Dog” who argued for compromise, by nearly 3 percentage points.

Ashford was seen by the Democratic Congressional Campaign Committee as a strong fit for a district that is slightly to the left of the nation’s average – voting for President Donald Trump by 2 points in 2016 and Mitt Romney by 7 points in 2012.

Now, the national party is left grappling with whether Eastman’s win will hurt their chances of ousting Republican Rep. Don Bacon, who had been seen as vulnerable in November.

Tuesday’s stunner in Omaha was a major primary victory for the left and underscored the momentum behind progressive and female candidates within the party, even as groups that have backed similar candidates, such as EMILY’s List for women and Sen. Bernie Sanders’ “Our Revolution” group for progressives, sat out the race.

A key question is how Eastman’s support for single-payer health insurance will play in Omaha, where the insurance industry is a key economic driver.

As a result of Eastman’s primary win, CNN is moving the race from “toss-up” to “Lean Republican.”

Eastman’s win comes after several near-misses, like progressive challenger Marie Newman falling just short of unseating Rep. Dan Lipinski – a rare anti-abortion Democrat – in Illinois in March.

The victory also came on a night that moderates fell in several other important races. In Pennsylvania’s Lehigh Valley, well-known district attorney John Morganelli lost a House primary to Susan Wild, an EMILY’s List-backed candidate well to his left. In a Philadelphia-area House primary, a self-funding progressive millionaire, Scott Wallace, defeated 33-year-old Navy veteran Rachel Reddick, who until 2016 was a Republican. The Democratic Socialists of America won several state legislative contests in Pennsylvania.

And John Fetterman, the tattooed, bearded and Sanders-backed mayor of Braddock just outside of Pittsburgh, unseated Pennsylvania’s sitting Democratic lieutenant governor, Mike Stack.

In Nebraska, Democrats now have to assess whether to invest heavily in Eastman against Bacon.

The Progressive Change Campaign Committee, which backed Eastman and hosted her at an advanced candidate training, cast her as the kind of candidate Democrats should nominate nationwide.

“Kara Eastman taught the Democratic establishment a lesson: The way to inspire voters in 2018 is to campaign on a bold progressive agenda of Medicare for All, higher wages for workers, and other economic populist ideas that help working families and challenge corporate power,” PCCC co-founder Stephanie Taylor said in a statement. “This is how Democrats can win in red, purple, and blue districts and maximize a wave in 2018.”

A DCCC aide praised Eastman as a wonkish candidate who brings significant accomplishments in her housing nonprofit, and noted that the primary never became negative, which helps avoid footage of Eastman’s own party’s members criticizing her. But Democrats will need to poll there to assess how Eastman matches up with Bacon, the aide said.

CNN’s Terence Burlij contributed to this report.