Democrat Joe Cunningham’s win in South Carolina’s 1st District is a blow to Republicans who thought they’d hold on to the coastal seat even after South Carolina Rep. Mark Sanford lost a GOP primary earlier this year. 

With 100 percent of precincts reporting, Cunningham led GOP state Rep. Katie Arrington 51 percent to 49 percent when The Associated Press called the race.

President Donald Trump carried this Charleston-area seat by 11 points in 2016. But there were signs the race was becoming increasingly competitive this fall, with some internal polling pointing to a close contest. Offshore drilling — which Sanford opposed and Arrington said during the primary that she supported — became a central part of the general election contest. 

National Republicans made a late investment on TV late in the final weeks to attack Cunningham. The Democrat, meanwhile, had attracted support from 314 Action, a group that supports scientists running for office. 314 Action’s political arm invested nearly $500,000, running ads on broadcast TV. The Democratic Congressional Campaign Committee had added Cunningham to its list of Red to Blue candidates for strong recruits in August. 

Cunningham outraised Arrington, who kicked personal money into her campaign. Cunningham did not self-fund and did not accept any money from PACs. He had the endorsement of End Citizens United but returned the Democratic PAC’s check. 

Arrington had defeated Sanford, a member of the House Freedom Caucus, in the June GOP primary. She’d secured the backing of Trump on primary day. While Sanford was a noted critic of the president, Arrington embraced him — perhaps too much for this district. Sanford declined to endorse her in the general election.

In a moment of major significance for this race, Arrington said during the primary that she supported Trump’s effort to lift the ban on offshore drilling. She repeatedly attempted to walk back those comments, but it became fodder for Cunningham and his allies. Cunningham picked up the endorsement of several area Republican mayors because of his opposition to offshore drilling. 

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