Elizabeth Colbert Busch, the sister of comedian Stephen Colbert, has won the Democratic nomination for a South Carolina House seat by a landslide, while the former state governor Mark Sanford will progress to a Republican run-off.

Polling took place on Tuesday in a US congressional primary race that threw together a colourful cast of candidates including Colbert Busch, whose brother joined her on the campaign trail; Ted Turner's son; and a former governor of the state who once gave new meaning to "hiking the Appalachian trail".