Updated at 9:48 p.m.

Former governor Mark Sanford won a Republican runoff election in South Carolina’s 1st congressional district on Tuesday, advancing to a head-to-head race against Democratic nominee Elizabeth Colbert Busch that early indicators suggest will be competitive.

The ex-governor defeated Curtis Bostic, a former Charleston County Council member, 57 percent to 43 percent.

Sanford was widely expected to defeat Bostic, whose campaign was dwarfed by the better-known and better-funded former governor. “It certainly has been a David and Goliath race,” Bostic said in a Monday interview.