President Trump
President Trump's candidate won the South Carolina Republican Senate primary Tuesday.

Lindsey Graham's sister Darline won the Tuesday Republican Senate primary and advanced to the general election in her bid to retain her late brother's South Carolina Senate seat.

Graham was appointed to the Senate seat by Gov. Henry McMaster after her brother's death in July. Graham, 62, will face Democrat Annie Andrews in the November general election and is expected to win.

Graham and Rep. Ralph Norman finished first and second in an Aug. 11 primary. She then defeated Norman in the Aug. 25 runoff.

Graham, a political neophyte, was helped by a strong endorsement from President Donald Trump. Trump rejoiced at Graham's win and also referenced his support of Mike Mazzei in the Republican primary for Oklahoma governor following the outcome.

"I supported and ENDORSED two so-called "underdogs" yesterday, one from South Carolina, and the other from Oklahoma, and they BOTH WON. Two great people!!!," Trump wrote on social media.

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Axios noted that Trump had campaigned with Graham on Friday and that MAGA Inc. spent more than $827,000 down the stretch to help her win.

Given how hard Trump had pushed for Graham, a defeat in the primary could have been politically damaging and shown that Trump's influence among Republicans was waning. Instead, Trump can point to the races as proof of how valuable his support can be within Republican politics.

"South Carolina, I am deeply honored and humbled to accept your nomination as the Republican candidate for the United States Senate," Graham said in a post on social media. "First and foremost, I thank the Lord for His blessings and guidance. To my family, President Trump, Team Graham, and the countless supporters across our state: thank you for believing in this mission and standing with us every step of the way."