Elaine Marshall has won the Democratic nomination to challenge North Carolina Sen. Richard Burr in November.
The veteran state leader defeated former Army prosecutor Cal Cunningham in Tuesday's election.
With 34 percent of precincts reporting, Marshall had 62 percent of the vote.
Marshall argued during her campaign that she has advocated on behalf of average citizens and fought against powerful industries. She portrayed herself as an outsider in the race despite holding statewide office for more than a decade.
Marshall's victory was a blow to Democratic Party leaders in Washington who recruited Cunningham to the race and spent more than $100,000 to boost his campaign.