The Latest on primaries in five states (all times EDT):
President Donald Trump is urging South Carolina Republican voters to dump frequent critic Rep. Mark Sanford.
Trump says Sanford "has been very unhelpful to me" and is poking fun at his infamous disappearance in 2009, when he was found to have been carrying on an extramarital affair with a woman in Argentina.
Trump tweets "he's better off in Argentina."
Sanford was elected during a 2013 special election to the U.S. House seat he had held previously despite the controversy which led to his divorce from his wife, Jenny.
He has called Trump untrustworthy and culturally intolerant, prompting Republican state Rep. Katie Arrington to challenge Sanford.
Trump tweeted his endorsement of Arrington along with the swipe at Sanford.
A bellwether Virginia congressional district promises to be among the most watched races nationally in primary elections in nearly every region of the country Tuesday.
President Donald Trump also will be a factor, notably in two Republican primaries in South Carolina.
South Carolina Gov. Henry McMaster has the president's backing but faces challenges from four other candidates. Republican Rep. Mark Sanford faces a challenge from a state lawmaker painting the outspoken former governor as insufficiently loyal to the president.
Elections are also scheduled in Maine, Nevada and North Dakota. Together, they raise to 21 the number of states having held their 2018 primary elections so far.