Political organizer Denise Powell has won the Democratic nomination in Nebraska’s 2nd District, NBC News projects, emerging from a tough primary fight in one of her party’s top opportunities to flip a swing seat this year. Powell narrowly defeated state Sen. John Cavanaugh in a race that featured five other Democratic candidates on the ballot. Powell had 39% to Cavanaugh’s 37% in the primary with about 90% of the expected vote tallied. She will advance to a general election matchup against Omaha City Council member Brinker Harding, who ran unopposed for the Republican nomination. Several major outside groups intervened in the primary. Powell, who was seen as the more moderate candidate, was backed by EMILY’s List, the Congressional Black Caucus, the Congressional Hispanic Caucus BOLD PAC and Elect Democratic Women. Cavanaugh, a progressive, was endorsed by the Congressional Progressive Caucus PAC, the Nebraska AFL-CIO and almost a dozen other local unions. State Sen.…