Voters head to polls in four states

Voters in Nevada, North Dakota, South Carolina and Maine are heading to the polls Tuesday in a series of closely watched primary elections that could help shape the balance of power in Washington.

(NBC)- Voters in Nevada, North Dakota, South Carolina and Maine are heading to the polls Tuesday in a series of closely watched primary elections that could help shape the balance of power in Washington.

One of the most closely watched contests is in Maine, where Democratic candidate Graham Platner is seeking the chance to challenge five-term Republican Senator Susan Collins in November.

Platner, an oyster farmer and former Marine, has emerged as the clear frontrunner in the Democratic primary. However, his campaign has faced scrutiny following allegations from three former girlfriends, who described what they called “toxic” and “unsettling” behavior in interviews with The New York Times.

Platner has denied the allegations while acknowledging he experienced a difficult period after his military service.

Meanwhile, President Donald Trump participated in a tele-rally supporting South Carolina Senator Lindsey Graham’s reelection campaign and again raised concerns about election integrity.

The president’s comments came after he abruptly ended an interview with NBC News’ Kristen Welker when challenged about his claims of voter fraud in California. There is no evidence of widespread voter fraud in the state’s ballot-counting process.

Trump later posted on social media that it was “not possible” for Los Angeles mayoral candidate Spencer Pratt, whom he endorsed, to lose his runoff race, alleging the election was rigged.

California election officials continue to defend the state’s vote-by-mail system, which can delay final results as ballots are processed and verified.

“Our job is to make sure we process those ballots securely, accurately and that does take time,” said Dean Logan, the Los Angeles County Registrar.

NBC News projects Los Angeles City Councilwoman Nithya Raman will face incumbent Mayor Karen Bass in the fall election.

Millions of mail-in ballots remain uncounted statewide in California, and the governor’s race remains too close to call. Both the Republican candidate and Governor Gavin Newsom’s office have expressed interest in speeding up the ballot-counting process, setting up a likely debate ahead of November’s election.