By Tim Reid and Gabriella Borter
PHOENIX, Ariz./BIRMINGHAM, Mich. (Reuters) -Control of Congress was up for grabs after Tuesday's U.S. midterm elections with many of the most competitive races uncalled, leaving it unclear whether Republicans would seize control from President Joe Biden's Democrats.
In a bright spot for Democrats, NBC News and Fox News projected John Fetterman won a critical U.S. Senate seat in Pennsylvania, beating Republican celebrity doctor Mehmet Oz and bolstering his party's chances of holding the chamber.
The mood at the White House improved as the night went on, with once-nervous aides allowing smiles to creep on their faces and saying early signs for Democrats were better than expected.
In the House of Representatives, Republicans had been favored to win a majority that would allow them to halt Biden's legislative agenda. By early Wednesday, the party had flipped four Democratic House seats, Edison Research projected, one short of the number they need to take over the chamber.
That number could change. Only 12 of the 53 most competitive races, based on a Reuters analysis of the leading nonpartisan forecasters, had been decided, raising the prospect that the final outcome may not be known for some time. Democrats were projected as the winners in 10 of those 12 contests.
The Senate was still a toss-up, with pivotal battles in Arizona, Georgia and Nevada still in play.
The Georgia Senate race could end up in a Dec. 6 runoff, possibly with Senate control at stake. Democrats currently control the 50-50 Senate with Vice President Kamala Harris able to break any ties.
Early results suggested Democrats would avoid the type of wipeout election that some in the party had feared, given Biden's sagging approval rating and voter frustration over inflation.
"Definitely not a Republican wave, that's for darn sure," Republican U.S. Senator Lindsey Graham told NBC in an interview. He held out hope that the party would take a majority in the Senate: "I think we're going to be at 51, 52, when it's all said and done."
Even a narrow Republican majority in the House would be able to block Biden's priorities while launching politically damaging investigations into his administration and family.
Thirty-five Senate seats and three dozen governors' races were also on the ballot. Florida Governor Ron DeSantis, a leading contender for the Republican presidential nomination in 2024, defeated Democratic Representative Charlie Crist, Edison projected.
More than 46 million Americans voted ahead of Election Day, either by mail or in person, according to data from the U.S. Election Project, and state election officials caution that counting those ballots will take time.
(Live election results from around the country are here.)
High inflation and abortion rights were voters' top concerns, with about three in ten voters picking one or the other as their top concern, exit polls showed. Crime, a major focus in Republican messaging in the campaign's final weeks, was the top issue for just about one in ten voters.
Both parties notched victories in competitive districts.
In Virginia's 2nd congressional district, Democratic U.S. Representative Elaine Luria lost to Republican challenger Jennifer Kiggans in a district Biden carried by two points. But in the state's 7th district, which Biden won in 2020 by 7 percentage points, Representative Abigail Spanberger held off a Republican challenger.
Local officials reported isolated problems across the country, including a paper shortage in a Pennsylvania county. In Maricopa County, Arizona - a key battleground - a judge rejected a Republican request to extend voting hours after some tabulation machines malfunctioned.
The problems stoked evidence-free claims among Trump and his supporters that the failures were deliberate.
Scores of Republican candidates have echoed Trump's false claims that his 2020 loss to Biden was due to widespread fraud. In Pennsylvania, Republican gubernatorial candidate Doug Mastriano, who sought to overturn the state's election results after Trump lost, was defeated by Democrat Josh Shapiro.
In New Hampshire, Democratic Senator Maggie Hassan prevailed over Republican Don Bolduc, a retired general who also backed Trump's baseless assertions, in a race that Republicans had once viewed as a top opportunity.
In swing states such as Arizona, Michigan and Nevada, the Republican nominees to head up the states' election apparatus have embraced Trump's falsehoods, raising fears among Democrats that, if they prevail, they could interfere with the 2024 presidential race.
"They deny that the last election was legitimate," Biden said on a radio show aimed at Black voters. "They're not sure they're going to accept the results unless they win."
Trump, who cast his ballot in Florida, has frequently hinted at a third presidential run. He said on Monday that he would make a "big announcement" on Nov. 15.
The party that occupies the White House almost always loses seats in midterm elections, and Democrats hoped the Supreme Court's June decision to overturn the nationwide right to abortion would help them defy that history.
But stubbornly high annual inflation, which at 8.2% stands at the highest rate in 40 years, has weighed on their chances throughout the campaign.
"The economy is terrible. I blame the current administration for that," said Bethany Hadelman, who said she voted for Republican candidates in Alpharetta, Georgia.
A Reuters/Ipsos poll this week found just 39% of Americans approved of the way Biden has done his job. Some Democratic candidates deliberately distanced themselves from the White House as Biden's popularity languished.
Trump's polling is similarly low, with just 41% of respondents to a separate recent Reuters/Ipsos poll saying they viewed him favorably.
In Congress, a Republican-controlled House would be able to thwart Democratic priorities such as abortion rights and climate change, while a Republican Senate would hold sway over Biden's judicial nominations, including any Supreme Court vacancy.
Republicans could also initiate a showdown over the country's debt ceiling, which could shake financial markets.
Republicans will have the power to block aid to Ukraine if they win back control of Congress, but analysts say they are more likely to slow or pare back the flow of defense and economic assistance.
(Reporting by Joseph Ax, Jason Lange, Doina Chiacu, Susan Heavey, Moira Warburton, Gram Slattery and Trevor Hunnicutt in Washington, Gabriella Borter in Birmingham, Michigan, Nathan Layne in Alpharetta, Georgia, Masha Tsvetkova in New York, Tim Reid in Phoenix and Ned Parker in Reno, Nevada; Writing by Joseph Ax and Andy Sullivan; Editing by Scott Malone, Alistair Bell, Daniel Wallis and Howard Goller)