The Republican Party has regained control of the US Senate, ending two years of Democratic leadership.

In Tuesday's general election, a third of the upper chamber of Congress – or 34 seats – took part in the vote, about nine of which were competitive.

Democrats were vulnerable to losing control of the chamber given their slim majority. A coalition of four independent senators and 47 Democrats gave the party its 51-member majority out of a total of 100 possible seats.

The party had to defend every possible seat to maintain control.

But on Tuesday, two decisive defeats put control of the Senate back in Republican hands.

Democratic incumbent Sherrod Brown has lost his bid for re-election in the Midwestern state of Ohio. Meanwhile, in West Virginia, Republicans captured a seat previously held by outgoing independent Sen. Joe Manchin.

The Republican Party also successfully defended a vulnerable Texas seat held by Sen. Ted Cruz. On Tuesday, Cruz defeated a Democratic candidate seeking to win his seat for the second time.

Meanwhile, in Nebraska, another Republican incumbent, Deb Fischer, fended off an upstart and independent candidate, Dan Osborn, who has made the race wobbly in recent weeks.

Shifting control of the Senate could pave the way for Republicans to represent both chambers of Congress, giving the party power over the legislative agenda for at least the next two years.

It also grants Republicans significant influence over nominations to the Supreme Court, the presidential cabinet, ambassadorships and other federal offices nominated by the president.

Republican presidential candidate Donald Trump commented on the chamber's about-face in his election night speech in West Palm Beach, Florida, in the early hours of Wednesday morning.

“We took back control of the Senate. “Wow,” Trump said. “I mean, the number of victories in the Senate was absolutely incredible.”

“Nobody expected that. No one. That's why I wanted to thank you very much for that. They have some great senators and some great new senators.”

What happened?

Tuesday's race to retain the Senate was always going to be an uphill battle for Democrats.

Under the U.S. Constitution, the Senate has a staggered process for restructuring its ranks: Only a third of the chamber is up for re-election at any given time.

Senators' terms are six years – much longer than the two years given to their colleagues in the House of Representatives. This makes every seat even more valuable.

In 2021, two runoff elections in Georgia gave Democrats their first lead in the House of Representatives since 2011.

Then, in 2022, the midterm elections caused another surprise. Although Republicans were expected to take control of the Senate, they failed when the predicted “red wave” failed to materialize.

In 2024, Democrats found themselves on the defensive. Seven of the nine Senate candidates were Democrats. In contrast, only two Republicans — Cruz and Fischer — were considered at risk.

In short, the Democrats had more to lose.

West Virginia, the first to fall

West Virginia has long been a Republican stronghold, making outgoing Sen. Manchin something of a unicorn.

Since 2000, the Appalachian state has always voted Republican by a significant margin in presidential elections.

But Manchin — a moderate Democrat before switching to his current independent status — had been a unifying figure in the state.

The announcement of his resignation in November 2023 sparked an exciting battle for Republicans.

Gov. Jim Justice, a Democrat-turned-Republican, quickly threw his hat into the ring. He won the West Virginia governor's mansion in 2016, the same year Republican Donald Trump took the White House, leading a wave of “outsider” candidates.

On Tuesday night, Justice — known for campaigning with a chubby bulldog named Baby Dog — soundly defeated Glenn Elliott, the Democratic mayor of the city of Wheeling.

A huge fall in Ohio

Three-term Democratic Senator Brown's defeat in Ohio was far more unexpected.

Until a few years ago, Ohio was considered a swing state in the industrial Rust Belt region of the USA. But as the state tilted to the right, Democratic leaders like Brown faced increasing threats to their positions.

As of 2024, Brown was the only Democrat still holding statewide office in Ohio.

On Tuesday, he tried to win a fourth term against Republican car dealer Bernie Moreno, a Colombian immigrant who received Trump's support.

Brown emphasized his progressive beliefs and criticized Moreno over abortion policies. He also portrayed himself as a politician willing to defy power, regardless of party.

“I have defied presidents of both parties,” he told local media during the campaign.

Moreno, meanwhile, called Brown a “radical Democrat” who is lax on immigration.

In his victory speech on election night, Moreno emphasized his patriotism – and repeated Trump's call for an “America First” policy.

“A new wave begins today. We talked about wanting a red wave. I think what we have tonight is a red, white and blue wave in this country,” Moreno said.

“Because what we need in the United States of America are leaders in Washington, DC, who will actually put the interests of the American people above all else. We are tired of being treated like second-class citizens in our own country.”

Al Jazeera correspondent Kristen Saloomey highlighted the magnitude of Ohio's loss for Senate Democrats.

“Ohio is the big turning point here. That’s the thing that really hurt Democrats,” she said on election night. “It was a really expensive race.”

Nebraska, less surprising

Located in the central prairies of the United States, Nebraska is known for electing Republican leaders. Although Electoral College votes are divided among districts, a majority of Electoral College votes have not gone to a Democrat for president since 1964.

It was expected that the Republican incumbent Fischer won his re-election on Tuesday. What was less expected was the close race she faced in the final weeks of her campaign.

A former school board member, Fischer had already served two terms in the Senate when she announced her re-election. But the entry of Osborn, a Marine veteran and union leader, into the race upended their winning ways.

During his campaign, Osborn rejected an offer of support from the Democratic Party and promised to remain strictly independent in his politics if elected.

He even declined to say whether he would align with Republicans or Democrats if he reached the Senate.

That made him a cipher in the race — a figure that disaffected Republicans could rally behind. He rose sharply in the polls and trailed Fischer by just percentage points in the final weeks of the race.

But Fischer tried to portray Osborn as “the same old Democrat nonsense” and “just another D.C. puppet,” as one campaign ad put it. She also accused him of being soft on immigration, a common call for Republicans this election cycle.

“Nebraska wasn’t really a surprise,” Saloomey said of the race, although she acknowledged that Osborn “made it close.”

Cruz survives in Texas

Texas has long been stubbornly Republican, and right-wing hothead Ted Cruz is just as stubbornly clinging to his Senate seat.

Cruz was first elected to the Senate in 2012 and was the first Latino from Texas to serve in the upper house of Congress. He was also a prominent member of the far-right Tea Party movement.

Democrats have failed to win a statewide vote in Texas since 1994. But that doesn't mean the party hasn't tried — and Cruz has often been in the crosshairs.

In his first re-election in 2018, Cruz faced a well-funded, charismatic Democratic challenger in former U.S. Rep. Beto O'Rourke. Despite a backlash against the far right in the middle of Trump's first term, Cruz scored a victory over O'Rourke.

In 2024, Cruz was seeking a third term, and once again Democrats tried to upset him.

This time they suggested U.S. Representative Colin Allred, a civil rights attorney and former American football player for the Tennessee Titans. Once again they failed.

“To God be the glory,” Cruz said in his victory speech on Tuesday. “Tonight is an incredible night, a huge win here in Texas.”

He also thanked “all Democrats across Texas who supported my campaign.”

“To everyone who didn’t support me: You have my word that I will fight for you, for your jobs, for your safety and for your constitutional rights.”