WASHINGTON — Pennsylvania Democrat John Fetterman has defeated Republican Dr. Mehmet Oz to flip a highly competitive Senate seat and sustain Democratic hopes of maintaining control of the upper chamber.

The win gives the party breathing room as it seeks to keep hold of its narrow Senate majority. It also serves as a major rebuke to former President Donald Trump, who endorsed Oz in his competitive GOP primary despite concerns over the celebrity heart surgeon’s limited ties to the state.

In his winning campaign, Fetterman overcame questions about his fitness for office after suffering a stroke just days before the state’s primary and struggling through his debate with Oz. He still has issues with auditory processing and uses closed-captioning technology to understand spoken words.

“I’m so humbled,” Fetterman, wearing his signature hoodie, told his supporters early Wednesday morning. “This campaign has always been about fighting for everyone whose ever been knocked down that ever got back up.”

Meanwhile democrats mounted a surprising show of strength on Wednesday as they repelled a series of Republican challengers in closely watched contests for Congress and governor’s mansions. Ultimately, control of Capitol Hill was unclear as votes were still being counted.

Democrats kept seats in districts from Virginia to Kansas and Rhode Island, while many districts in states like New York and California had not been called.

Democratic House Speaker Nancy Pelosi said early Wednesday, “While many races remain too close to call, it is clear that House Democratic Members and candidates are strongly outperforming expectations across the country.” Rep. Kevin McCarthy, the Republican poised to be House speaker if the GOP takes control of the chamber, had not yet addressed supporters.

Democrats held a crucial Senate seat in New Hampshire, where incumbent Maggie Hassan defeated Republican Don Bolduc, a retired Army general who had initially promoted former President Donald Trump’s lies about the 2020 election but tried to shift away from some of the more extreme positions he took during the GOP primary. Republicans held Senate seats in Ohio and North Carolina.

The outcome of races for House and Senate will determine the future of President Joe Biden’s agenda and serve as a referendum on his administration as the nation reels from record-high inflation and concerns over the direction of the country. Republican control of the House would likely trigger a round of investigations into Biden and his family, while a GOP Senate takeover would hobble Biden’s ability to make judicial appointments.

Democrats were facing historic headwinds. The party in power almost always suffers losses in the president’s first midterm elections, but Democrats had been hoping that anger from the Supreme Court’s decision to gut abortion rights might energize their voters to buck historical trends.

In Pennsylvania, Democratic Attorney General Josh Shapiro beat Republican Doug Mastriano to keep the governorship of a key presidential battleground state blue. Shapiro’s victory rebuffed an election denier who some feared would not certify a Democratic presidential win in the state in 2024. Democrats Gretchen Whitmer of Michigan, Kathy Hochul of New York, Michelle Lujan Grisham of New Mexico and Janet Mills of Maine also repelled Republican challengers.

Incumbent Republican governors also had success. Georgia Gov. Brian Kemp won reelection, defeating Stacey Abrams in a rematch of their 2018 race. Florida Gov. Ron DeSantis and Texas Gov. Greg Abbott, two future possible Republican presidential contenders, beat back Democratic challengers to win in the nation’s two largest red states.

In Georgia, Democratic Sen. Raphael Warnock and Republican challenger Herschel Walker were vying for a seat that could determine control of the Senate.

AP VoteCast, a broad survey of the national electorate, showed that high inflation and concerns about the fragility of democracy were heavily influencing voters.

Half of voters said inflation factored significantly, with groceries, gasoline, housing, food and other costs that have shot up in the past year. Slightly fewer — 44% — said the future of democracy was their primary consideration.

Overall, 7 in 10 voters said the ruling overturning the 1973 decision enshrining abortion rights was an important factor in their midterm decisions.

VoteCast also showed the reversal was broadly unpopular. About 6 in 10 say they are angry or dissatisfied by it, while about 4 in 10 were pleased. And roughly 6 in 10 say they favor a law guaranteeing access to legal abortion nationwide.

There were no widespread problems with ballots or voter intimidation reported around the country, though there were hiccups typical of most Election Days.