Washington — Nevadans are voting Tuesday in the Senate primaries as Republicans are set to nominate a candidate to take on incumbent Democratic Sen. Jacky Rosen come November, when the balance of the Senate will be up in the air. 

Republicans haven't won a Senate race in the Silver State since 2012. And it's been even longer, since 2004, that a Republican presidential candidate has won Nevada. But Republicans flipped the governor's mansion in the last election, and recent polls have shown former President Donald Trump with a slight edge over President Biden, suggesting that the state's races could be seriously in play for the GOP. 

Meanwhile, Democrats face steep odds of holding the majority in the Senate. Democrats and Democratic-leaning independents have a slim, 51-seat majority at present that they are fiercely working to defend. But this cycle poses major obstacles, with Democratic senators up for reelection in a handful of states that Trump won in 2020. And in another five states considered battleground states — like Nevada — Democrats' reelection isn't guaranteed.

For Rosen, this year marks her first reelection bid. The former synagogue president unseated a Republican incumbent in 2018, after one term in the House. But whether the moderate Democrat can hold on to the seat in November is an open question.

Though a long list of Republicans are running in Tuesday's GOP primary, businessman and former army captain Sam Brown is widely seen as the GOP frontrunner. And perhaps adding to his prospects was a last-minute Trump endorsement over the weekend. 

Trump stopped short of a full-throated endorsement of Brown during a Las Vegas rally on Sunday, calling Brown a "good man" after months of praising multiple GOP candidates and teasing an endorsement more recently. But hours later, the former president took to his social media platform to clarify that "Sam Brown has my Complete and Total Endorsement," adding that he's "already proven his Love for our Country, being horrifically wounded, and making the Comeback of a Lifetime."

Brown was awarded a purple heart for his service in Afghanistan, where he sustained third-degree burns across a portion of his body. He has the backing of the bulk of the GOP, including Nevada Gov. Joe Lombardo. But there are other Republicans, like former ambassador to Iceland Jeff Gunter, who are giving Brown a run for his money in Tuesday's primary.  

Gunter, who worked under the Trump administration and has the backing of some of the former president's allies, has tried to position himself as close to Trump throughout his campaign, calling himself "110% pro-Trump." And the strategy may have been helped by the former president's delay in weighing in on the race. Whether Trump's endorsement, which came after early voting had ended in the state, cements Brown's victory remains to be seen. 

"Looking at the timing of this endorsement, obviously it's too late to have the kind of impact that it could have had, because a whole bunch of Nevadans have already cast their ballots," says Rebecca Gill, a political science professor at the University of Nevada, Las Vegas. "If his intent was to help Sam Brown win, he would have made this endorsement a while ago."

Looking toward the general election, a survey conducted in late April by Emerson College found Rosen leading Brown 45% to 37% in a hypothetical matchup. And the incumbent saw a larger lead against Gunter. 

Still, Nevada has historically posed polling difficulties, with high population turnover. 

"It's really difficult to poll here in Nevada, because people move around so much," Gill said. "So this just makes it, I think, a lot more unsettled going into the election about how close the race really is, who's really up."

Indeed, the race has appeared to grow increasingly close. In April, the Cook Political Report changed its rating from "lean Democrat" to "toss-up," noting in an analysis that "unique forces" are at play in Nevada, including a newer electorate, the president's lagging poll numbers and a tourism-reliant economy still struggling to bounce back after the pandemic.

Nevada's economy, heavily reliant on tourism and hospitality, was among the most impacted by pandemic closures in 2020. And the job market in Las Vegas in particular was among the hardest hit in the nation, leading to a much slower recovery than in other states. For Nevadans, economic issues that have struck a chord with the nation more broadly, like inflation prices and housing prices, are particularly relevant. 

In 2022, Republicans benefited from former Gov. Steve Sisolak's unpopular COVID-19 policies, as Lombardo hit the Democrat hard on COVID-related closures. But Senate races have a different dynamic and Sen. Catherine Cortez Masto managed to survive.

Cortez Masto's race for Nevada's other Senate seat was among the closest in the country. But the Democrat ultimately won her reelection bid against former Nevada attorney general Adam Laxalt, who had bested Brown in the primaries. Republicans are betting on Brown being a stronger candidate this cycle, while Rosen's name brand doesn't run as deep as her counterpart in the Senate, who served as Nevada's attorney general before coming to the Senate. 

But turnout could change the dynamic from Cortez Masto's election during the midterms, when turnout is generally suppressed. And whether people in Clark County, home to liberal voting blocs in Las Vegas, turnout will be key for Democrats. 

"People in Clark County don't tend to come out to vote in as high of numbers when there's not a presidential race on the ballot. And so that depression and turnout for Clark County can make it more difficult for Democrats in statewide elections," Gill said. But she added that voter fatigue and low enthusiasm in this particular presidential election could "make this race incredibly tight."

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Kaia Hubbard

Kaia Hubbard is a politics reporter for CBS News Digital, based in Washington, D.C.

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