Primaries were held Tuesday in Virginia, South Carolina, Maine, Nevada and North Dakota. In the Maine races, voters tried out a new type of voting, ranked choice voting. It allows voters to pick their candidates in order of preference.
Here are some of the notable results from Tuesday's races:
South Carolina: Mark Sanford loses to Trump-backed candidate
Rep. Mark Sanford, a vocal critic of President Trump, lost his South Carolina congressional seat hours after the president injected himself into the bitter Republican primary by stoking memories of the incumbent's public extramarital affair several years ago.
In the most dramatic result in primaries across five states Tuesday, Sanford was the second incumbent House Republican to lose a primary this year - and the latest victim of intense divisions among the GOP in the Trump era.
Though he has a generally conservative voting record, his criticism of Mr. Trump as unworthy and culturally intolerant made him a target of the president's most dedicated supporters, who often elevate loyalty over policy.
Sanford was defeated by state Rep. Katie Arrington , who spent her campaign blasting Sanford as a "Never Trumper."
And hours before polls closed, Mr. Trump posted a startlingly personal attack on Twitter, calling Sanford "very unhelpful."
"He's MIA and nothing but trouble," the president continued. "He is better off in Argentina."
The swipe was a reference to Sanford's unexplained disappearance from the state in 2009, which he later said was part of an affair he was carrying on with a woman in Argentina.
Even for a political figure with no shortage of confidence wading into his own party's decision-making, Mr. Trump's attack on Sanford was a bold case of going after a sitting member of Congress. It's almost certain to make other Republicans even more reluctant to take him on, even as Trump has stirs division on trade, foreign policy and the Russia investigation.
In remarks Tuesday night, Sanford was unbowed, saying, "I stand by every one of those decisions to disagree with the president."
Sanford had never lost a political race in South Carolina and his defeat Tuesday was an abrupt end to a roller-coaster political career that included a resignation as South Carolina's governor following his admission of the affair.
After declaring victory Tuesday, Arrington asked Republicans to come together. And she reminded them who she thinks leads them: "We are the party of President Donald J. Trump."
Wednesday morning, the president tweeted about the outcome, saying, "My political representatives didn't want me to get involved in the Mark Sanford primary thinking that Sanford would easily win - but with a few hours left I felt that Katie was such a good candidate, and Sanford was so bad, I had to give it a shot. Congrats to Katie Arrington!"
Sanford was not the only establishment Republican to face a challenge Tuesday. South Carolina Gov. Henry McMaster, a close ally of Mr. Trump, was forced into a runoff after failing to muster the required 50 percent vote to win outright.
McMaster, an early supporter of the president's 2016 campaign, had Mr. Trump's full endorsement, marked by a weekend tweet.
But while the president remains very popular in the state, McMaster has been shadowed by a corruption probe involving a longtime political consultant. McMaster received the most votes of the four Republicans running, but will face Greenville businessman John Warren in a second contest June 26.
McMaster, the former lieutenant governor, assumed the governorship last year after Nikki Haley resigned to become U.S. ambassador to the United Nations.
Virginia: Trump backer wins GOP Senate nod
In a big Virginia race , Republican Corey Stewart - known for his ardent defense of Confederate symbolism - won the Republican primary to face Democratic Sen. Tim Kaine.
President Trump weighed in on Twitter Wednesday morning, saying, "Congratulations to Corey Stewart for his great victory for Senator from Virginia. Now he runs against a total stiff, Tim Kaine, who is weak on crime and borders, and wants to raise your taxes through the roof. Don't underestimate Corey, a major chance of winning!"
Stewart surprised many by nearly winning last year's Republican nomination for governor. He was the top aide to Donald Trump's presidential campaign in Virginia in 2016, but was fired for staging an unauthorized protest of the Republican National Committee. Stewart had accused the party of inadequately defending the candidate after the release of a tape in which Mr. Trump bragged about groping women.
As a candidate for governor in 2017, Stewart spoke out against removing Confederate monuments, including the Robert E. Lee statue that prompted a deadly protest in Charlottesville last year. Stewart called efforts to remove the monuments "an attempt to destroy traditional America." He said Tuesday he planned to wage a "vicious" campaign against Kaine.
Kaine is seeking a second term, though he wasn't on the ballot Tuesday. The former governor and 2016 vice-presidential nominee became his party's nominee in March, when no other Democrats filed to run against him. So, unlike Republicans, Virginia Democrats did not need a primary Tuesday in the Senate race.
Elsewhere in the state, Democratic State Sen. Jennifer Wexton was the clear winner in a six-way primary in a northern Virginia district considered key to the House battleground map this fall, and will challenge Republican Rep. Barbara Comstock.
Democrats in two other districts they hope to retake nominated women: Abigail Spanberger in central Virginia and Elaine Luria in the district that includes Virginia Beach.
In Comstock's district, Wexton was the best-known in the field, and was viewed as the Democratic Party's establishment choice. She had the endorsement of Democratic Gov. Ralph Northam.
Comstock, a moderate Republican who easily beat back a challenge from conservative Shak Hill, is one of the Democrats' top targets in November. The second-term House member's district leans Republican, though Democrat Hillary Clinton received more votes there than Mr. Trump did in 2016.
Though Wexton favors a ban on the sale of assault weapons, she defied what has been the tendency in some swing districts to nominate Democrats with liberal profiles on other key issues. She has not called for a single-payer, government-run health insurance system, as some Democratic House primary winners in California, Nebraska and Pennsylvania have.
Democrats need to gain 23 seats to win the majority in the House.
North Dakota: Kevin Cramer wins GOP Senate primary
U.S. Rep. Kevin Cramer has defeated a little-known opponent to win North Dakota's Republican primary for U.S. Senate.
Cramer easily beat Air Force veteran Thomas O'Neill on Tuesday. Cramer now faces a tougher campaign to unseat Democratic Sen. Heidi Heitkamp in a race seen as critical for control of the closely divided Senate.
Cramer is a former state Republican Party chairman. He was first elected to the House in 2012 and has easily won re-election twice since then.
Cramer initially passed up the Senate race this year but said he changed his mind at the urging of President Trump and others who saw him as the GOP's best hope to defeat Heitkamp.
The other notable statewide race was the GOP battle for the House seat Cramer is vacating.
Republican state Sen. Kelly Armstrong has won North Dakota's U.S. House primary. Armstrong is vying to replace Cramer.
Armstrong easily defeated former Marine Tiffany Abentroth and former North Dakota State football player Paul Schaffner.
State Sen. Tom Campbell also appeared on the ballot despite dropping out of the race. Armstrong, an attorney from Dickinson, has strong ties to the state's oil industry. He'll face Democrat Mac Schneider, a Grand Forks attorney who had no opposition in the primary. Schneider served two terms in the North Dakota Senate before being unseated in 2016.
Nevada: Trump-backed candidate wins congressional race
Danny Tarkanian has won the Republican primary for Nevada's 3rd District congressional seat left open by the incumbent Democrat who's running against GOP Sen. Dean Heller in November. The son of former UNLV basketball coach Jerry Tarkanian will face Las Vegas Democrat Susie Lee in the high stakes battle that is expected to be the most expensive congressional race in Nevada this fall. Lee clinched the Democratic nomination Tuesday.
Both candidates raised well over $1 million in their primary campaigns. Tarkanian didn't enter the House race until March, when President Trump and others persuaded him to abandon an aggressive bid to knock off Heller in the Senate primary. The incumbent congresswoman, Jacky Rosen, won the Democratic Senate nomination Tuesday for the right to challenge Heller in November.
Steve Sisolak, a Nevada politician backed by former Sen. Harry Reid, won a contentious Democratic primary for Nevada governor. Sisolak, chairman of the Clark County Commission, bested his commission colleague, Christina Giunchigliani, and four other candidates Tuesday.
He's expected to face Republican state Treasurer Adam Laxalt in the November election.
Nevada hasn't had a Democratic governor in two decades. Moderate Republican Gov. Brian Sandoval is leaving the office because he is term-limited.
Heller is the only GOP senator seeking re-election in a state won by Democrat Hillary Clinton in 2016, was originally expected to face a tough challenge from Republican Danny Tarkanian until Mr. Trump asked him to run for Congress instead.
Also in Nevada, pimp Dennis Hof, owner of half a dozen legal brothels in Nevada and star of the HBO adult reality series "Cathouse," won a Republican primary for state Legislature, ousting a three-term lawmaker.Voters in November will also be voting on closing down brothels in at least one of the seven Nevada counties where they're legally operating, and activists are trying to get the measure on the ballot in another district.
Maine: Democrats eye Polquin's seat
Maine voters are deciding on a successor to term-limited, firebrand conservative Republican Gov. Paul LePage. But first they had to wrestle with a new balloting system.
Maine on Tuesday debuted its statewide ranked-choice voting , which allows voters to rank candidates first to last on their ballot. The system insured that counting would be slow and winners difficult to call.
But businessman Shawn Moody won the GOP nomination after midnight. He maintained a wide lead through the night, but risked not winning the race outright under the new rules.
The Associated Press did not call the Democratic primary, as none of the seven candidates was close to the majority needed to be declared the outright winner, so more tabulations are required next week under ranked-choice voting. Last-place candidates will be eliminated and votes reallocated until there is a winner, a process that may take more than a week.