Rep. Jacky Rosen Jacklyn (Jacky) Sheryl RosenHillicon Valley: Election officials prepare for new Russian interference battle | 'Markeyverse' of online fans helps take down a Kennedy | GOP senators unveil bill to update tech liability protections Google, Apple, eBay to meet virtually with lawmakers for tech group's annual fly-in Senate Democrats demand answers on migrant child trafficking during pandemic MORE (D) has defeated Sen. Dean Heller Dean Arthur HellerOn The Trail: Democrats plan to hammer Trump on Social Security, Medicare Lobbying World Democrats spend big to put Senate in play MORE (R) in Nevada's toss-up Senate race, giving Democrats a win in one of their few pickup opportunities of the cycle.

Heller, who was running for a second term, conceded the race shortly before it was called by The Associated Press. A spokesman for Heller's campaign didn't immediately respond to a request for comment.

Rosen's victory in Nevada marks a major win for Senate Democrats in an otherwise rough election night, with Republicans poised to expand their Senate majority after unseating several red-state Democrats. The state was also a bright spot for the party in 2016 when Democrats swept the state.

ADVERTISEMENT

“When it came time to elect a Senator who would stand up for Nevadans, the choice was clear. Jacky Rosen has always stood out because of her commitment to serve her community, and now her state - and do what is right even if it’s hard. We need more problem solvers like Jacky and I look forward to welcoming her to the U.S. Senate," said Sen. Chris Van Hollen Christopher (Chris) Van HollenCongress must finish work on popular conservation bill before time runs out Democrats fear Russia interference could spoil bid to retake Senate Mid-Atlantic states sue EPA over Chesapeake Bay pollution MORE (D-Md.), the chairman of the Democratic Senatorial Campaign Committee.

Rosen's victory will make Nevada only one of seven states that has been represented by two female senators simultaneously.

"Women are winning up and down the ballot. This is a historic night for us," Rosen said in a speech claiming victory early Wednesday morning.

Republicans argued that the deck was stacked against them after Democrats swept the state in 2016 and have dedicated years to building a strong turnout machine.

Steven Law — the president of the Senate Leadership Fund, which has ties to Majority Leader Mitch McConnell Addison (Mitch) Mitchell McConnellPelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Senate GOP aims to confirm Trump court pick by Oct. 29: report Trump argues full Supreme Court needed to settle potential election disputes MORE (R-Ky.) — said that group spent more than $16 million in the state to try to "make it a fair fight."

"We wish Senator Heller well and hope he continues to stay engaged in Nevada politics in the future," he said.

Nevada was one of the most closely watched races in the country and among one of the most expensive Senate races, according to the Center for Responsive Politics. Democrats made Heller a top target early on because he was the only Republican senator running for reelection in a state won by Hillary Clinton Hillary Diane Rodham ClintonButtigieg stands in as Pence for Harris's debate practice Senate GOP sees early Supreme Court vote as political booster shot Poll: 51 percent of voters want to abolish the electoral college MORE.

Heller embraced Trump — after describing himself as “99 percent against” him in the 2016 election — as part of his 2018 strategy. He campaigned with the president and touted Republicans' ability to confirm his Supreme Court picks.

Heller was able to keep the race close despite getting hit with more than $33 million in outside money opposing him.

But there were signs that the race was slipping away from him in the waning days of the midterm election. Though he and Rosen seesawed throughout the election, an Emerson College Poll released Monday found Rosen with a 4-percentage point lead.

He was also under pressure to drive up his margin among independents and rural voters, after Democrats led in early voting by 3.5 percentage points and Jon Ralston, a veteran Nevada political observer, predicted Heller's defeat.

Updated: 3:18 a.m.