"Now, we're just in a very weird place that I've never seen before", Sanford said.
"He is MIA and nothing but trouble", Trump said.
Trump doubled down on the tweet on Wednesday, saying he had to get involved in the race because Sanford was "so bad". His public confession came after Sanford disappeared from the governor's office, and a spokesman said he was "hiking the Appalachian Trail", when he was actually visiting his mistress.
Archie Parnell of Sumter, who almost won the 5th District's seat in the U.S. House for Democrats in a 2017 special election, was left for dead by party leaders in May after news broke that he had physically abused his ex wife in the 1970s.
Caleb Frostman, the Democrat running in Wisconsin State Senate District 1, claimed victory in Tuesday's special election and Frostman's campaign manager, Hannah Akbik, told CNN that Republican Andre Jacque conceded the race in a phone call with the Democrat.
"We are the party of President Donald J. Trump", Arrington said to her backers.
Sanford was not the only sitting member to receive the Trump Twitter treatment as the head of the Republican Party - clearly on a high from his historic meeting with the North Korean leader - returned to the White House.
Throughout his political career, Sanford has played up his outsider credentials - both in the US House, where he supported a box to check on federal tax returns to put $3 toward the national debt, and as governor, bringing a pair of squealing pigs to the state House and Senate chamber to protest what he called pork spending. That was a snarky reference to Sanford's adulterous affair when he was governor, in 2009, from a president who has been identified as an alleged adulterer.
Another Republican who was also critical of Trump, Alabama GOP Rep. Martha Roby, is also at risk of losing re-election. In July 2016, shortly after wrapping up the Republican nomination and hoping to unify the party before the convention, Trump paid a high profile visit to congressional Republicans on Capitol Hill.
Arrington, a businesswoman with ties to the military, was considered an underdog when she initially launched her first race for Congress previous year. He is better of in Argentina.
The Democratic victor was Susie Lee, a philanthropist who previously lost a primary in the nearby 4th Congressional District and had locked up most party support. The president's record of keeping his promises resonates across the district.
Sanford's loss was perhaps the most dramatic result in primaries across five states Tuesday. After Trump's win in November 2016, he appointed then-Gov.
Golden was leading late Tuesday.
While fealty to the Republican president may be a requirement to win low-turnout Republican primaries dominated by conservative activists, it could prove a tougher sell against energized anti-Trump Democratic forces in midterm elections this fall. Tim Kaine and choosing nominees in several competitive House races, Nevada and North Dakota choosing their Senate candidates and ME for the first time trying - and voting on whether to keep - a new voting system in which voters rank their preferences, rather than only selecting one. Luria, a Navy veteran and businesswoman, was her party's pick in the contest for the seat held by Republican Representative Scott Taylor, who's a former Navy SEAL. The second-term House member's district leans Republican, though Democrat Hillary Clinton received more votes there than Trump did in 2016.