The left says its populist message can attract moderates and conservatives in addition to liberals. That theory will be put to the test in a series of competitive races on Election Day.

© The New York Times

The left says its populist message can attract moderates and conservatives in addition to liberals. That theory will be put to the test in a series of competitive races on Election Day.

© The New York Times

Matt Dunlap defeated a candidate backed by the House Democratic campaign arm and is set to face former Gov. Paul LePage, a Republican, in a competitive general election.

© Graeme Sloan/Getty Images

No candidate cleared 50 percent in the Democratic primary race to replace Representative Jared Golden, sending the race into ranked-choice voting.

A mysterious group has spent $500,000 to elevate a progressive candidate in the Democratic primary race for a key House seat.

© John Tully for The New York Times