Sen. Jacky Rosen, D-Nev., speaks to supporters during an election watch party Wednesday, Nov. 6, 2024, in Las Vegas. (AP Photo/John Locher)

WASHINGTON (AP) — Democratic incumbent Sen. Jacky Rosen won reelection early Saturday morning after The Associated Press declared she had beat Republican Sam Brown in a race that turned on Rosen's strong performance in the state's two largest counties — Clark and Washoe.

With nearly all of the vote counted, the AP called the race for Rosen.

At the time the AP called the race at 12:15 a.m. ET on Saturday, there were not enough votes left to count, according to AP's estimates, in the state's rural areas to make up the gap created by Rosen's performance in the counties that are home to Las Vegas and Reno.

Rosen was one of several vulnerable Senate Democrats defending their seats with control of the chamber hanging in the balance. By the time Rosen was named the winner, the GOP had long since won control of the Senate and she will return to Washington as a member of the minority party.

The AP declares a winner only when it can determine that a trailing candidate can’t close the gap and overtake the vote leader.

Here’s a look at how the AP called this race:

CANDIDATES: Rosen (D) vs. Brown (R) and two others plus “None of these candidates.”

POLL CLOSING TIME: 10 p.m. ET

ABOUT THE RACE: Rosen was one of five vulnerable Senate Democrats running for reelection in a cycle when a loss by any one of them could have cost their party control of the chamber, given the Republican pick-up of the retiring Sen. Joe Manchin’s seat in West Virginia earlier on election night.

Rosen was first elected in 2018, when she defeated Republican incumbent Dean Heller by 5 percentage points. Brown ran unsuccessfully for the GOP nomination for the state’s other U.S. Senate seat in 2022, placing a distant second in a crowded field behind Adam Laxalt. He is a retired Army captain who was nearly killed by a roadside bomb in Afghanistan. Rosen more than doubled Brown’s spending and fundraising haul for the cycle, but both entered the final two-and-a-half week stretch of the campaign about evenly matched in terms of available cash in the bank.

In statewide elections, Democrats tend to carry only two of Nevada’s 17 counties: Clark (home to Las Vegas) and Washoe (home to Reno). Whether they win depends on how big their margins are in those two counties. Clark County has by far the largest population in the state. A large vote margin there is vital to Democratic electoral success. It comprised 69% of the total statewide vote in 2020. Washoe is more competitive.

WHY AP CALLED THE RACE: In vote results reported after Election Day, Rosen has consistently won every update released by election officials in Clark and Washoe counties. There’s no precedent in recent Nevada elections for ballots counted late in the process in those counties to back a Republican, and at the time of AP’s race call, there were not enough ballots left in the state’s rural counties to make up for her edge in Clark and Washoe.

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Learn more about how and why the AP declares winners in U.S. elections at Explaining Election 2024, a series from The Associated Press aimed at helping make sense of the American democracy. The AP receives support from several private foundations to enhance its explanatory coverage of elections and democracy. See more about AP’s democracy initiative here. The AP is solely responsible for all content.

News from © The Associated Press, 2024