The Democrats have kept control of the US Senate for two more years, dashing Republican hopes of a wave sweeping them into majority.
The fate of the House of Representatives was still uncertain as the GOP struggled to pull together a slim majority there.
Senator Catherine Cortez Masto’s victory in Nevada gave Democrats the 50 seats they needed to keep the Senate.
Her win reflects the surprising strength of Democrats across the US this election year.
Seeking re-election in an economically challenged state that has some of the highest gas prices in the nation, Ms Cortez Masto was considered the Senate’s most vulnerable member, adding to the frustration of Republicans who were confident she could be defeated.
Senate Majority Leader Chuck Schumer claimed victory on Saturday night, tweeting: “Your Senate Democratic Majority!”
With the results in Nevada now decided, Georgia is the only state where both parties are still competing for a Senate seat.
Democratic incumbent Senator Raphael Warnock faces GOP challenger Herschel Walker in a December 6 runoff.
Alaska’s Senate race has advanced to ranked choice voting, though the seat will stay in Republican hands.
Democratic control of the Senate ensures a smoother process for President Joe Biden’s Cabinet appointments and judicial picks, including those for potential Supreme Court openings.
The party will also keep control over committees and have the power to conduct investigations or oversight of the Biden administration, and will be able to reject legislation sent over by the House if the GOP wins that chamber.
If Democrats manage to pull off a win in the House, it would mean full control of Congress for Democrats — and another chance to advance Mr Biden’s priorities, which he has said include codifying abortion rights.
The party still lacks the 60 votes in the Senate needed to move many kinds of major legislative changes.
The Senate fight had hinged on a handful of deeply contested seats.
Both parties spent tens of millions of dollars in Pennsylvania, Arizona, Nevada and Georgia, the top battlegrounds where Democrats had hoped that Republicans’ decision to nominate untested candidates — many backed by former President Donald Trump — would help them defy national headwinds.
Democrats scored a big win in Pennsylvania, where Governor John Fetterman defeated celebrity heart surgeon Dr Mehmet Oz, who was endorsed by Donald Trump, to pick up a seat currently held by a Republican.
Arizona Senator Mark Kelly won re-election by about five percentage points.
A closely divided swing state, Nevada is one of the most racially diverse in the nation, a working-class state whose residents have been especially hard-hit by inflation and other economic turmoil.
Roughly three-fourths of Nevada voters said the country is headed in the wrong direction, and about half called the economy the most important issue facing the country, according to AP VoteCast, a survey of 2,100 of the state’s voters.
Heading into the midterm election, Republicans focused relentlessly on the economy, a top concern for many voters amid stubborn inflation and high gas and food prices.
The GOP also hit Democrats on crime, a message that sometimes overstated the threat but nonetheless tapped into anxiety, particularly among the suburban voters who turned away from the party in 2018 and 2020.
And they highlighted illegal border crossings, accusing Biden and other Democrats of failing to protect the country.
But Democrats were buoyed by voters angry about the Supreme Court’s June decision overturning the constitutional right to an abortion.
They also portrayed Republicans as too extreme and a threat to democracy, following the January 6 2021 insurrection at the US Capitol and Mr Trump’s false claims — repeated by many GOP candidates — that the 2020 election was stolen from him.
Nationally, VoteCast showed that seven in 10 voters said the Supreme Court’s decision on Roe v Wade was an important factor in their midterm decisions.
It also showed the reversal was broadly unpopular. And roughly six in 10 said they favour a law guaranteeing access to legal abortion nationwide.
Half of voters said inflation factored significantly in their vote, while 44% said the future of democracy was their primary consideration.
Beyond Congress, Democrats won key governors’ races in Wisconsin, Michigan and Pennsylvania — battlegrounds critical to Biden’s 2020 win over Trump.
Republicans, though, held governors’ mansions in Florida, Texas and Georgia — another battleground state Biden narrowly won two years ago.
Though the midterms failed to deliver Republican romps, Trump remains a major factor in the national party and plans to announce a third run for the presidency on Tuesday at his Mar-a-Lago estate in Florida — setting up a potential rematch for the White House with Biden.