In the most dramatic result in primaries across five states, Sanford was the second incumbent House Republican to lose a primary this year - the latest victim of intense divisions among the GOP in the Trump era.
Trump endorsed Arrington hours before the polls closed Tuesday in a tweet attacking Sanford for being "very unhelpful to me in my campaign to MAGA". That refers to 2009, when Sanford's aides said he was hiking the Appalachian Trail while he actually visited a woman with whom he was having an affair in Argentina.
But Trump saved his first two tweets while back in the National Capital District's airspace for the now-departing SC congressman - and his opposition of Sanford exposed a rare chasm between himself and conservative Republicans.
South Carolina Republicans expressed their discontent during primary voting Tuesday as President Donald Trump sought to influence the race.
He demurred during the run-up to the 2016 election when asked if he'd support Trump and spoke out against the president after the election on issues such as limiting Muslim immigrants.
The president himself weighed in by stoking memories of the affair, tweeting that Sanford was "better off in Argentina".
Also on Tuesday, House Republican leaders averted a rebellion by moderates seeking to end-run Speaker Paul Ryan and force votes on legislation opposed by Trump that would give young undocumented immigrants a path to citizenship. "The playing field of ideas that many of us came into in the class of '94.it's devolved to: are you for or against the President, are you for or against Trump?"
Sanford had represented the Charleston district on and off for six terms, with eight years in the Governor's Mansion in between. With 99 percent of precincts reporting, she had 50.6 percent of the vote to Sanford's 46.5 percent.More news: Who, where and when do England play in Russian Federation ?
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He was sacked from the Trump campaign after staging an unsanctioned protest at the headquarters of the Republican National Committee, which Stewart said wasn't sufficiently loyal to Trump during the presidential campaign.
Trump congratulated Corey Stewart, his onetime Virginia campaign chairman and an immigration hardliner, for winning a GOP primary that will put him against incumbent Democratic Sen.
"Primary voters in the Republican Party have devolved into a Trumpist cult".
'She is tough on crime and will continue our fight to lower taxes. "He is better off in Argentina", the president wrote.
In Virginia, two women will compete for a suburban Washington congressional district seen as key to Democrats' hopes of retaking the House majority in November.
Sanford said those statements "may have cost me an election in this case, but I stand by every one of those decisions to disagree with the president".
Nevada also has an interesting governor's race, with six Democrats and seven Republicans vying to run for a position that's been controlled by the GOP for almost 20 years.
He said Tuesday he planned to wage a "vicious" campaign against Kaine.
Sanford has held the seat since a special election in 2013, but faces a tight challenge in the GOP primary from Arrington, a first-term S.C. House member. Democrat Hillary Clinton carried it over Trump by 10 percentage points in the 2016 presidential election.