Washington DC - Democrats picked up a seat in the Senate on Tuesday when pediatrician Annie Andrews narrowly defeated Darline Graham, who was seeking to permanently fill her late brother Lindsey Graham's shoes, media projections showed.

Andrews stunned Darline Graham, who temporarily filled the seat after her brother's death in July but turned out not to be as strong a candidate as her party – or President Donald Trump – had hoped.

NBC News and CNN called the race in Andrews's favor.

Graham was appointed to the Senate by South Carolina Governor Henry McMaster after Trump recommended her for the role.

US politics Midterms: Voters lean toward stinging rebuke of Trump as Democrats flip major Senate seat

The president described the appointment as a "fabulous tribute" to her late brother, a prominent foreign-policy hawk and close Trump ally.

Lindsey Graham – who served in the House of Representatives before winning election to the Senate in 2002 – never married or had children and was exceptionally close to his sister.

Their mother died when Lindsey Graham was 20, and his sister was 12, followed less than two years later by their father's death from a heart attack.

Lindsey Graham, then 22, formally adopted his 13-year-old sister, helped her finish school and largely raised her.

While her brother was an influential voice on foreign policy issues, Darline Graham struggled when asked about Taiwan during a recent debate, admitting that she was "not that informed on national security."

She was still able to defeat veteran Congressman Ralph Norman to secure the Republican nomination, with Trump campaigning for her and urging supporters to vote as though his own name were on the ballot.