In South Carolina's 1st District, which has been red since 1981, Joe Cunningham, an ocean scientist, defeated the Republican hopeful Katie Arrington.
Cunningham, who is also a lawyer, sparred with Arrington throughout the campaign over the future of offshore drilling. His expertise in this area won over the Republican mayors of the coastal cities of Folly Beach and Isle of Palms.
Arrington, who has served in South Carolina's House of Representatives, does not oppose offshore drilling. She emphasized national issues such as immigration and President Donald Trump's proposed wall along the US-Mexico border, while Cunningham focused on local issues.
Cunningham won the race by 4,036 votes, a margin of 1.4 percentage points. An outcome with a margin of 1 percentage point or less would have triggered an automatic recount.