Incumbent Mark Sanford, who returned after affair scandal, loses in SC primary Maine, Nevada, North Dakota, South Carolina and Virginia hold primaries Tuesday.

Voters in Maine, Nevada, North Dakota, South Carolina and Virginia headed to the polls Tuesday, as the 2018 primary season continues its steady march towards the first major election since the inauguration of President Donald Trump.

Twenty-five U.S. House seats, four U.S. Senate seats, and three governor's seats were at stake in the states holding primaries Tuesday, and Democrats are eyeing a number of purple districts in Virginia as they look to map out their path to retaking the lower chamber in November.

But the biggest news likely came in South Carolina, where Rep. Mark Sanford bounced back from an infamous affair scandal only to lose in Tuesday's Republican primary over questions of his support for Trump. The president tweeted about Sanford's defeat just minutes after landing back in Washington, D.C., upon return from Singapore.

The Commonwealth of Virginia also played host to a nasty GOP primary for the U.S. Senate, largely revolving around loyalty to Trump, a theme that continues to resurface throughout the primary season in a bevy of Republican races across the country.

Eight female candidates have already emerged victorious in governors races in the 15 states that have held gubernatorial primaries so far this year, a tally that is likely to rise Tuesday. Female gubernatorial candidates in Maine, Nevada and South Carolina are hoping to continue the success women are seeing on the ballot across the country.

Republicans are eyeing North Dakota, one of the 10 states Trump won in the 2016 election with an incumbent Democratic senator, as a top pickup opportunity with Sen. Heidi Heitkamp up for re-election. Democrats are countering by targeting Nevada, the lone state in the nation with a GOP incumbent in a state Hillary Clinton won in 2016, Sen. Dean Heller.

Polls closed in South Carolina and Virginia at 7 p.m. ET, in Maine at 8 p.m. ET, in North Dakota at 9 p.m. ET, and in Nevada at 10 p.m. ET.

Here's our live blog of the evening of news ...

12:10 a.m. -- Sanford officially loses to primary challenger, Sisolak victorious in Nevada

It's official -- 10 minutes after midnight The Associated Press has projected that Mark Sanford has lost to primary challenger and Trump-aligned candidate Katie Arrington.

The loss officially makes Sanford the second sitting member of Congress to lose a primary this cycle.

In Nevada, the AP projected that Clark County Commission Chair Steve Sisolak has defeated fellow Clark County Commissioner Chris Giunchigliani in the Democratic primary for governor. The result is a win for Nevada political titan and former Democratic U.S. Senate leader Harry Reid, who backed Sisolak and poured a substantial amount of his own money into the race, and a loss for EMILY's List and Hillary Clinton, who backed Giunchigliani.

Check back in Wednesday morning for any other major updates from another fascinating 2018 primary night.

From all of us at ABC News Politics, goodnight!

11:20 p.m. -- Nevada Senate race is Heller vs. Rosen, Lee wins in key swing district

We're (hopefully) winding down another eventful primary night.

In Nevada's U.S. Senate race there were no primary surprises -- it will be Democratic Rep. Jacky Rosen taking on GOP Sen. Dean Heller.

Heller is the only incumbent Republican senator in a state Hillary Clinton won in the 2016 presidential election.

State Attorney General Adam Laxalt breezed through the Republican gubernatorial primary on the heels of an endorsement earlier today from President Donald Trump.

Nonprofit executive Susie Lee, a Democrat running in Nevada's 3rd Congressional District -- which was vacated by Rosen due to her U.S. Senate bid -- easily won the primary in this suburban Las Vegas swing district, and will likely face businessman Danny Tarkanian in November.

Tarkanian, the son of legendary UNLV basketball coach Jerry Tarkanian, dropped his U.S. Senate bid against Heller earlier this year at the urging of Trump.

10:50 p.m. -- AP: Sanford tells supporters "I'm going to lose this race"

Republican Rep. Mark Sanford appears to be the second sitting Member of Congress to lose a primary in 2018.

According to The Associated Press and local news reports, Sanford told a crowd of supporters in South Carolina tonight that based on the current numbers, "I'm going to lose this race."

The video below was taken by Caitlin Byrd, a reporter for the Post & Courier, a Charleston-based newspaper.

The AP has not made an official projection in the race, but Sanford's words indicate there is little chance of him mounting a comeback against primary challenger state Rep. Katie Arrington.

10:35 p.m. -- Sanford awaits his fate

It's getting late ... and the outlook is not improving for GOP Rep. Mark Sanford, who's fighting for his political life against primary challenger Katie Arrington.

Arrington, a state representative, is currently leading Sanford 51.2 percent to 45.8 percent, according to election returns from the South Carolina Secretary of State.

If that margin holds, Arrington would automatically advance to the November general election, and Sanford would become the second sitting Member of Congress to lose a primary this year -- the other being North Carolina GOP Rep. Robert Pittenger last month.

The development would be another stark reminder of the effect Trump, who tweeted earlier today bashing Sanford, is having on this uniquely chaotic midterm cycle.

10:05 p.m. -- NRSC declines to comment on Corey Stewart's victory

The U.S. Senate race in Virginia is set, and the drama has already begun.

Firebrand conservative Corey Stewart, a self-described "Trump loyalist," won the GOP nomination to take on Democratic Sen. Tim Kaine, but the national campaign arm of Senate Republicans isn't ready to show its support for Stewart.

The National Republican Senatorial Committee eclined to comment on Stewart's victory when reached Tuesday night by ABC News.

10:00 p.m. -- Polls close in Nevada

And with that, polls in all five states have closed tonight.

The marquee races in the Silver State include the Democratic primary for governor, and the open seats races in the state's 3rd and 4th congressional districts.

Here's to hoping Nevada counts its votes fast ...

9:45 p.m. -- McMaster headed to a runoff in South Carolina governors race, Parnell wins despite abuse admission

With it appearing unlikely that incumbent Gov. Henry McMaster will receive a majority of the vote in South Carolina's Republican gubernatorial primary, the Associated Press projects he will face fellow Republican John Warren in a primary runoff. As of the time of the call, McMaster, the state's former lieutenant governor who succeeded Nikki Haley when she resigned to become ambassador to the U.N., led businessman John Warren 44.3-25.5.

In one additional South Carolina race we had our eye on, Democrat Archie Parnell is projected to win his party's primary in the 5th congressional district. Parnell performed better than expected -- though still lost to Republican Ralph Norman -- in last year's special election to replace now-OMB director Mick Mulvaney, but faced controversy recently when he admitted to abusing his ex-wife 45 years ago.

Trump won SC-05 by 18.5 percent in 2016. The first round of Norman-Parnell in 2017 went to Norman (R) by just over 3 percent.

9:25 p.m. -- Kaine reacts to Stewart's victory in GOP primary

Virginia Sen. Tim Kaine now has a general election opponent, and he is not mincing his words.

"Corey Stewart stokes white supremacists," Kaine told ABC News' Benjamin Siegel at a victory party for State Sen. Jennifer Wexton, who won the Democratic nomination in Virginia's 10th Congressional District earlier tonight.

Kaine also hit Stewart for his willingness to fully embrace President Trump.

"They’re running not to be any kind of a check on the executive, they're running to be President Trump's yes man," Kaine said, "That's not what we need in the Senate and that's not who Virginia is."

9:06 p.m. -- Kaine, Wexton look ahead to a general election battle in Northern Virginia

Democrats in northern Virginia moved one step closer to flipping Rep. Barbara Comstock's seat and reclaiming the House in November, after State Sen. Jennifer Wexton cruised passed five opponents to win the primary Tuesday night, ABC News' Benjamin Siegel writes from inside the room at Wexton's victory party.

The race is expected to be one of the most competitive and expensive in the country. Sen. Tim Kaine, who introduced Wexton and is running for reelection in November, set the stakes for supporters, warming up the crowd for Wexton by citing Democrats’ performance in the state last fall.

"Just like Virginia sent the nation a message of hope last November ... we will be part of demonstrating what real American values are," he said.

Wexton hit on the GOP tax plan, gun control and health care as she rallied supporters, previewing some of the themes of the general election. She also appeared to reference the president, promising to “get back to the better angels of our nature.”

“The people are ready for change,” she said to applause, before her campaign started playing Jennifer Lopez’s hit “Jenny From the Block.”

9:00 p.m. -- Polls close in North Dakota

And, with that, the polls have closed in four out of five states voting Tuesday night.

There's not much drama expected in North Dakota, but Democratic Sen. Heidi Heitkamp is high on the list of incumbents the GOP is targeting this year. Her opponent will be GOP Rep. Kevin Cramer.

8:51 p.m. -- Trump ally Corey Stewart wins GOP primary for U.S. Senate

Now, the calls are coming in fast and furious.

In one of the key races of the night, Trump ally Corey Stewart, who promised a "vicious" campaign against Democratic Sen. Tim Kaine, has won the GOP primary for U.S. Senate.

Stewart, who was almost the Republican nominee for Virginia governor in 2017, barely edged out State Del. Nick Freitas for the nomination.

Stewart labeled Freitas #NeverTrumpNick and accused him of "race-baiting" throughout the primary after Freitas called into question Stewart's associations with the white supremacist group involved in the violence in Charlottesville, Virginia, last year.

8:38 p.m. -- Women sweep competitive Virginia House primaries

In the three Democratic primaries taking place in Virginia U.S. House district that are potentially competitive in November, female candidates are reigning supreme.

Wexton's victory Tuesday in one of ABC News' "18 for 18" races is notable as it was projected earlier than Comstock who had a closer-than-expected fight for an incumbent against challenger Shak Hill, who ran to the right of the moderate-leaning Comstock. When the race was called, the spread between Comstock and Hill was less than 5,000 votes.

Republican Rep. Scott Taylor secured his party's nomination in Virginia's 2nd District, a district Trump won by only three points in 2016, and therefore a Democratic target. Democratic Gov. Ralph Northam won the district by four points last year. Taylor will face Democrat Elaine Luria, a 20-year Navy veteran, and nuclear engineer.

In Virginia's 7th Congressional District, Democrat Abigail Spanberger, a former CIA operations officer, is projected to win her primary. Spanberger will be facing Rep. Dave Brat, best known for his insurgent, Tea Party-backed primary campaign in 2014 that took down House Majority Leader Eric Cantor in the district. Trump won VA-07 by six in 2016.

Democrats previously nominated filmmaker and activist Leslie Cockburn, the mother of actress Olivia Wilde, as their candidate in Virginia's 5th Congressional District, another race that could be competitive in November.

ABC News' MaryAlice Parks has much more from these formidable women.

8:06 p.m. -- Democratic State Sen. Jennifer Wexton projected the winner in Virginia's 10th Congressional District

It's one of the key districts Democrats are hoping to flip in their quest to retake the U.S. House in 2018, and, now, they have a candidate.

The Associated Press projected state Sen. Jennifer Wexton, who had the endorsement of Virginia Gov. Ralph Northam and the Washington Post editorial board, the winner of the Democratic primary in the 10th District.

ABC News' Benjamin Siegel reports that cheers were going up at Wexton's victory party in Sterling, Virginia.

8:00 p.m. -- Polls close in Maine, where a new voting system is on the ballot

It's 8 p.m. in the east, and polls have just closed in the state of Maine, where voters will select their candidates via an emerging system known as ranked-choice voting, which, ironically, could face its elimination on the same day it is finally utilized in a statewide race for the first time.

ABC News' Adam Kelsey has more on the implication of tonight's voting.

Voters are also casting their ballots in competitive primaries for governor in both parties. Maine's often controversial GOP Gov. Paul LePage is term-limited.

7:30 p.m. -- GOP primary to take on Tim Kaine a close contest

Results are just beginning to trickle in across the Commonwealth of Virginia, but early returns show a close race for the GOP nomination to take on Democratic Sen. Tim Kaine (Hillary Clinton's veep pick).

State Delegate Nick Freitas and Prince William County Board of Supervisors Chairman Corey Stewart are running one-two right now, while Conservative minister and attorney E.W. Jackson is in a distant third.

Freitas has made Stewart's associations with the white nationalist group behind the Charlottesville protests last summer an issue in the race.

But Freitas himself ignited controversy with comments he made on the floor of the Virginia House of Delegates in March suggesting that mass shootings in the U.S. are due to the "abortion industry" and "broken homes."

ABC News' Adam Kelsey notes that both of Kaine's statewide victories have been close. Here are results from his 2012 Senate bid and 2005 gubernatorial run:

Virginia Senate 2012 Tim Kaine (D) - 52.9 George Allen (R) - 47.0

Virginia Gubernatorial 2005 Tim Kaine (D) - 51.7 Jerry Kilgore (R) - 46.0

7:00 p.m. -- polls close in South Carolina in Virginia

Finally, polls have closed in two states: South Carolina and Virginia.

Expect first results to roll in soon, and you can monitor live results in Virginia right here.

6:35 p.m. -- Trump endorses Laxalt in Nevada governor race, while Hillary Clinton backs 'Chris G'

Is it 2016, again?

Both Trump and Clinton made endorsements in the race to be the Silver State's next governor, with Trump endorsing state Attorney General Adam Laxalt in a tweet this morning, and Clinton recording a robocall for Democratic candidate Clark County Commissioner Chris Giunchigliani over another Clark County Commissioner Steve Sisolak.

The race also pits former Democratic U.S. Senate leader Harry Reid's political machine, which is backing Sisolak, against the might of EMILY's List and other groups who are backing "Chris G."

Nevada hasn't had a Democratic governor since the 1990s, but its recent streak of wins in the state on the presidential level has the state seeing blue in 2018. Incumbent GOP Gov. Brian Sandoval, a popular figure in the state and a potential future presidential contender, is term-limited.

6:00 p.m. -- One hour away from the first polls closing

The anticipation of primary night drama is growing nearer.

We're just one hour out from poll closings in South Carolina and Virginia.

Obviously, recent developments in Rep. Mark Sanford's re-election bid in the Palmetto State's 1st Congressional District make that race one to watch but don't forget to keep an eye on the governor race there as well, where incumbent Gov. Henry McMaster is likely headed to a runoff election.

Stay tuned for much, much more...

4:30 p.m. -- Mark Sanford's re-election bid just got a lot more interesting

Nothing like a last minute presidential tweet to inject more drama into one of Tuesday's most high-profile races.

Sanford represents a deep red district, but the latest tweet from Trump endorsing his primary opponent, State Rep. Katie Arrington, further complicates things for the former South Carolina governor who was forced into political exile after he lied about an extra-marital affair in 2009, only to return to politics two years later, winning a Charleston-based congressional seat.

If neither Sanford nor Arrington receives 50 percent of the vote Tuesday, they will head to a runoff election in just two weeks time.

2:00 p.m. -- Democrats test anti-Trump messages in Virginia House race

One of Tuesday's marquee races is the Democratic primary in Virginia's 10th Congressional District, located in the suburbs just south of Washington, D.C.

There are six Democrats vying for the chance to unseat Republican Rep. Barbara Comstock, a political survivor who faces another tough race this cycle given that Clinton won her district by 10 points in the 2016 presidential election.

Despite being an eclectic mix, all the Democrats in the race point to Trump -- his conduct in and out of office as much as his administration’s policies -- as a key factor in their decisions to run for Congress.

ABC News' Benjamin Siegel has more on this key race.

12:45 p.m. -- Tuesday highlights record number of women running for office in 2018

According to Rutgers University’s Center for Women and American Politics, an eye-popping 455 women filed to run for Congress this election cycle, far surpassing the previous record set in 2012, when 298 women ran. Five months into this primary season, after 21 states have voted, 116 women have won their primaries and will be on general election ballots in the fall.

Those numbers are poised to rise Tuesday.

ABC News Deputy Political Director MaryAlice Parks features a few of the women running in the states holding primaries Tuesday, including Abigail Spanberger in Virginia's 7th Congressional District, and Elaine Luria in Virginia's 2nd Congressional District.

11:30 a.m. -- In Maine, casting ballots with, and on, ranked-choice voting

Voters in Maine head to the polls Tuesday as their state joins four others in holding primary elections, but unlike those casting ballots in Nevada, North Dakota, South Carolina and Virginia -- Mainers will select their candidates via an emerging system known as ranked-choice voting, which, ironically, could face its elimination on the same day it is finally utilized in a statewide race for the first time.

Ranked-choice voting was approved by Maine voters in 2016 after a string of 11 gubernatorial races in which the ultimate winner received a majority of the vote -- over 50 percent -- just twice.

In the other nine instances, including both general election victories by incumbent Gov. Paul LePage, the winner received a plurality of the vote -- the highest total among multiple candidates but less than 50 percent.

ABC News' Adam Kelsey reports.

8:00 a.m. -- Tuesday's primaries center on Trump, control of Congress

Want to read in on all of the key races tonight? The ABC News Politics team has you covered.

From a nasty Republican primary for U.S. Senate to an ideological struggle among Democrats vying to be the next governor of Nevada, Tuesday's primaries offer a wide array of storylines and characters to watch.

Read more on the top contests Tuesday from ABC News' John Verhovek, Adam Kelsey and Benjamin Siegel.

6:00 a.m. -- The Note: Trump, Kim relationship based on trust -- and how to verify

Unsurprisingly the headlines this morning were not dominated by the states holding primaries on this Tuesday in early June, they were all focused on the historic summit between Trump and the reclusive leader of North Korea Kim Jong-Un.

With one handshake the two leaders gave the world an image never seen before.

But as ABC News Political Director Rick Klein writes: Beyond the handshakes and the photo ops, the flags, the logos, the special video, the closing statement and the "message of peace," President Donald Trump and Kim Jong Un have constructed something critical and tenuous in Singapore where they need something valuable and often fleeting from each other: trust.

But while the world woke up transfixed on the news of the Trump-Un summit, Americans in five states woke up to an Election Day!

Top of mind today is the Commonwealth of Virginia.

It was roughly seven months ago that the Democratic hopes of a "Blue Wave" sweeping them back into power in the U.S. House first took shape in the form of a historically strong performance in the Commonwealth of Virginia -- where the party not only cemented their control on the governor's mansion but also nearly retook the state House of Delegates for the first time in almost 20 years, writes ABC News Political Reporter John Verhovek.