The congressman, former governor and one-time presidential aspirant was trailing a little-known state lawmaker who slammed him for his repeated criticism of President Trump, the latest sign that the most unsafe thing to do in the modern GOP is dare to take on the president.
Voters also cast ballots in Maine, Nevada and North Dakota, as the field for the mid-term elections begins to take shape.
Sanford has at times criticized Trump and didn't back off that criticism in debates with Arrington. But I'm guessing that the endorsement put Arrington over the top. "Also, will fight hard to lower your taxes and is tough on crime!"
Rematches: In 2014, Nevada politics watchers were shocked when Democratic congressman Steven Horsford, a rising political star, lost his outer Las Vegas area district to an unpolished newcomer, Republican Cresent Hardy.
But in Virginia, Democrats are selecting House candidates to run in some of the nation's most competitive races. He'll face Senator Tim Kaine, the Democratic incumbent.
In Virginia's 2nd Congressional District, Democrat and veteran Elaine Luria will face incumbent Republican Rep. Scott Taylor, also a veteran.
The South Carolina race highlighted primary voting in five states on Tuesday.
In Nevada, the parties will choose their nominees in two competitive open seats. The second-term House member's district leans Republican, though Democrat Hillary Clinton received more votes there than Trump did in 2016.
The Senate landscape is becoming more settled Tuesday night as well.
President Donald Trump has congratulated his loyalist Corey Stewart for winning Virginia's Republican Senate primary. None of the three Senate candidates appears to match that region.
As S.C. governor, his rigid ideological conservatism made him a favorite of tea party Republicans while putting him at odds with state lawmakers over spending.
In most states voting Tuesday night, the governor races will get the most local attention.
In South Carolina, Republican Gov. Henry McMaster - an early and vocal supporter of Trump who replaced former Gov. Nikki Haley - fell short of 50% and is headed to a June 26 runoff with the second-place finisher, businessman John Warren.
Arrington will take on Joe Cunningham, a construction lawyer and yoga studio owner who won the Democratic nomination Tuesday. Tuesday demonstrated yet again just how strong the anti-incumbency mood is among Republican primary voters.
Sisolak, 64, is chair of the powerful governing body for Clark County, which includes the Las Vegas Strip and about two-thirds of the state's residents.But Giunchigliani paints Sisolak as too moderate and has knocked him for receiving an "A-" minus rating from the National Rifle Association in 2012. He also supported Nevada Attorney General and GOP gubernatorial candidate Adam Laxalt.