Ellmers already started the 2016 cycle with a couple cracks in her hold on the seat.

In 2014, local activists were angry over her support for giving undocumented immigrants earned legal work status, and she received a primary challenge. She defeated Frank Roche, a radio host whom Republicans called a weak and underfunded challenger, with 58 percent of the vote.

Republicans say Duncan, a retired businessman who ran a computer disaster recovery company, is a more serious candidate than Roche. Duncan has better ties to the conservative base in the district, both because of his role as chairman of the Chatham County Republican Party and as a co-founder of the Coalition for American Principles, a group that seeks to elect Republicans in the Raleigh-Durham area.