The top races to watch are centered in Nevada, with key congressional and state contests, and in South Carolina, which has U.S. House incumbents being challenged by Republicans who have the endorsement of former President Donald Trump.
Here's what we're keeping an eye out for:
Nevada Senate race
Incumbent Democratic Sen. Catherine Cortez Masto will likely have a tough race in November against whichever candidate wins the GOP primary. Cortez Masto's seat is considered a toss-up by forecasters, adding pressure on Democrats, who are trying to maintain their slim Senate majority.
Laxalt has received Trump's endorsement and the backing of Florida Gov. Ron DeSantis. Laxalt, who was a Nevada co-chair of Trump's 2020 campaign, has been heavily leaning on Trump's early support, and has been an outspoken advocate for Trump's lie that the 2020 election was stolen from him.
The former president held a tele-rally for Laxalt last week, telling supporters that Laxalt winning would be a birthday present to Trump, whose birthday is Tuesday.
The primary isn't locked down yet, though. Businessman and retired Army Capt. Sam Brown has moved up in polling in the last few weeks of the race. Brown has also raised more small-dollar donations than Laxalt and is spending more on television ads.
Nevada gubernatorial race
Nevada's GOP gubernatorial primary is another race to watch. Whoever wins Tuesday night will face off against incumbent Democratic Gov. Steve Sisolak, who came into office by beating Laxalt by 4 percentage points in 2018.
Joe Lombardo, the sheriff of Clark County, where Las Vegas is located, is the Trump-endorsed candidate in the race and has had a healthy lead in surveys.
Among those behind Lombardo in surveys are Joey Gilbert, an attorney and former boxer; former Sen. Dean Heller, who lost to current Sen. Jacky Rosen in 2018; and North Las Vegas Mayor John Lee.
Nevada secretary of state
Nevada is another swing state where Republican candidates who've repeated baseless claims about the 2020 election are now running to oversee elections.
The most notable candidate in the GOP field is Jim Marchant, a former member of the state Assembly who's said the 2020 election was stolen from him (in a congressional race) and Trump. He's also pushed for doing away with voting machines, returning to hand-counting ballots — something election experts say is a bad idea.
Other candidates include Jesse Haw, Richard Scotti, Gerard Ramalho and Kristopher Dahir, a Sparks city councilor who's pushed back against fraud claims but has also been critical of Democratic-led voting changes in the state.
On the Democratic side, Cisco Aguilar is running unopposed. The current secretary, Barbara Cegavske, is term-limited. The Republican was censured by the state GOP back in April 2021 for not doing enough to investigate alleged election fraud.
Nevada congressional races
Nevada's congressional map underscores Democrats' precarious hold on the state. Three of its four congressional seats are held by Democrats and are considered by the nonpartisan Cook Political Report to be general election toss-ups.
In the 1st District, Rep. Dina Titus is first up against progressive candidate Amy Vilela, who received Vermont Sen. Bernie Sanders' endorsement just last week. Several candidates are seeking to emerge from the Republican side.
The state's 3rd District is represented by Democratic Congresswoman Susie Lee. She faces a challenge within her own party from Randell Hynes. On the GOP side there are five candidates running, with lawyer and business owner April Becker getting endorsements from the Nevada Republican Party and House Minority Leader Kevin McCarthy, R-Calif.
In the 4th District, three Republicans are facing off to determine who will challenge Rep. Steven Horsford in November. The National Republican Congressional Committee has backed Nevada Assemblywoman Annie Black in the GOP race.
South Carolina’s 7th and 1st Congressional Districts
In the Palmetto State, Trump's picks are rooted in revenge.
Republican Rep. Tom Rice in the state's 7th Congressional District voted to impeach the former president after the Jan. 6 insurrection and now he's facing a challenge from 37-year-old state Rep. Russell Fry, among others.
"He said he's been following our work at the Statehouse, from election integrity to the heartbeat bill to the open carry bill we passed last year," Fry said of Trump in February, when he received his endorsement.
Rice — one of just 10 House Republicans to vote for Trump's impeachment — has stood by that vote.
In the 1st District, Rep. Nancy Mace faces a challenge from Katie Arrington, who Trump backed. While Mace did not vote to impeach Trump, she was critical of his actions on Jan. 6, saying he "put all of our lives at risk." Just that was enough for Trump to back her primary opponent.
In South Carolina, a candidate needs to get more than 50% of the vote to avoid a June 28 runoff.
Maine's 2nd Congressional District
Democratic Rep. Jared Golden will likely face another tough fight in November, against whichever candidate wins the GOP primary Tuesday night.
Republican voters will choose between former Rep. Bruce Poliquin and Liz Caruso, a local leader who says she aligns politically with far-right Republicans like Georgia's Marjorie Taylor Greene and Ohio's Jim Jordan.
Poliquin lost his reelection bid in 2018 to Golden by about 1 percentage point, but the district went for Trump both in 2016 and 2020.
Independent candidate Tiffany Bond filed enough signatures to also make the ballot.
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