Democrat Annie Andrews is within striking distance of flipping South Carolina's Senate seat as Lindsey Graham's sister Darline stumbles

Democrat Annie Andrews, a paediatrician running in South Carolina, has closed to within single digits of Republican incumbent Darline Graham ahead of Tuesday's vote, with internal polls showing a race once regarded as a foregone conclusion turning genuinely competitive. Trump's endorsement of Darline Graham is pushing away independent voters and right-flank supporters of Rep. Ralph Norman, who resent the president's intervention in what they see as a state-level decision.

Andrews could become the first Democrat to win a South Carolina statewide race since 1998 — nearly three decades of Republican dominance.

Darline Graham, by her own admission 'a little nervous', was a political newcomer thrust into the race after her brother Lindsey Graham died in July seeking his fifth Senate term.

The winner will make history as the first woman South Carolina has ever sent to the US Senate.