But Arrington has hammered Sanford for his criticism of President Donald Trump, and she enough GOP voters in the district may agree with her. "He is better off in Argentina", the president wrote, referring to Sanford's trip to South America in 2009 to have an affair while his unknowing staff in the governor's office told reporters he was hiking the Appalachian Trail.
The Republican also served two terms as the governor of SC. In Alabama, U.S. Rep. Martha Roby is in a July 17 runoff against former congressman Bobby Bright.
With 98% of the vote counted, USA media called the race for state representative Katie Arrington, who led Sanford by 50.5% to 46.5%.
McMaster was an early supporter of President Donald Trump, and he was the top vote-getter in Tuesday's primary.
Democrat Jennifer Wexton won a six-way primary race and will take on Republican Barbara Comstock, one of the Democrats' top targets in their push to pick up the 23 seats they need to claim a majority in the House.
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"It's fairly unusual for a president to tweet in a congressional race".
He tweeted: "Mark Sanford has been very unhelpful to me in my campaign to MAGA".
"They don't want the tweet that I got last night", Sanford said. In a February 2017 Politico piece, he said Trump has "fanned the flames of intolerance".
'I'm not looking for disagreement with the administration, ' Sanford told Politico. "He is better off in Argentina", Trump tweeted.
Arrington's campaign was based on the premise that Sanford - who has criticized Trump's style and questioned his knowledge - is insufficiently supportive of the President.
In North Dakota, Rep. Kevin Cramer won the Republican nomination for Senate and will face Democratic incumbent Heidi Heitkamp, who had no primary challenger. McMaster was one of the few established Republicans in the state to back Trump in 2016, and became governor when Trump named Nikki Haley as United Nations ambassador.
The district, which stretches up past Green Bay along Wisconsin's northern peninsula, has traditionally been Republican, with the GOP incumbent who ran in 2014 winning with 62% of the vote. In North Dakota, GOP Representative Kevin Cramer was declared the party's primary victor, setting him up to run against Democratic Senator Heidi Heitkamp. "I mean it's nearly becoming a cultish thing", Senator Bob Corker, a retiring Tennessee Republican, told reporters Wednesday, a day after lambasting other GOP lawmakers on the floor of the Senate for being too afraid of Trump to rein in his authority to impose tariffs.
Sanford was not the only establishment Republican to face challenges Tuesday.
In Nevada, Democrats are set to nominate Rep. Jacky Rosen to take on Republican Sen.