(CNN)-- President Donald Trump said Monday that he recommended South Carolina Governor to appoint the sister of the late Senator Lindsey Graham to fill his Senate seat, after his sudden death over the weekend.

Trump wrote on Truth Social: "I have recommended Governor Henry McMaster to appoint Darlene, the sister of the wonderful Lindsey Graham, as an interim Senator for the great state of South Carolina. This would be a wonderful tribute to Lindsey, who loved her very much!"

Graham was close to his sister, Darlene Graham Nordon. The late Senator became her legal guardian when he was in his early 20s, after the death of their parents within 15 months.

The late Senator, then in his early 20s, became the legal guardian of his sister.

Under state law, McMaster is entitled to appoint an interim replacement to fill Graham's vacant seat.

But because Graham was a candidate for reelection this year, his death will trigger a quick primary election to select a replacement for him on the November ballot.