People vote at a fire station in the midterm elections on Nov 8, 2022, in Hialeah, Florida. (LYNNE SLADKY / AP)

WASHINGTON/PHOENIX, Arizona/BIRMINGHAM, Michigan – Senate incumbents including Democratic leader Chuck Schumer and senior Republican John Thune won re-election in Tuesday's US midterm elections, on a day Republicans were expected to wrest control of Congress away from President Joe Biden's Democrats.

Thirty-five Senate seats and all 435 House of Representatives seats are on the ballot. Republicans are widely favored to pick up the five seats they need to take over the House, but control of the Senate could come down to tight races in Pennsylvania, Nevada, Georgia and Arizona.

Three dozen governors' races are at stake as well; Florida Governor Ron DeSantis, a possible contender for the Republican presidential nomination in 2024, defeated Democratic Representative Charlie Crist, Edison Research projected.

The final outcome, particularly control of the 50-50 Senate, is unlikely to be known any time soon. Democrats currently control that chamber through Vice-President Kamala Harris' tie-breaking vote.

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In a competitive House race in Virginia, Democratic Representative Jennifer Wexton held off a challenge by Republican Hung Cao.

More than 46 million Americans voted ahead of Election Day, either by mail or in person, according to data from the US Election Project, and state election officials caution that counting those ballots will take time. The Georgia race could end up in a Dec 6 runoff to determine which party holds the Senate.

Local officials reported isolated problems across the country, including a bomb threat in Louisiana and 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 former President Donald 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 swing states such as Nevada, Arizona and Michigan, 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.

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"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.

Biden was expected to watch the results from the White House, where the usually quiet corridors were abuzz with aides. A Biden adviser, anticipating a tough evening, said Democrats had done the best they could given higher gas prices and inflation.

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Economic worries

The party that occupies the White House almost always loses seats in midterm elections, but Democrats had hoped the Supreme Court's June decision to overturn the nationwide right to abortion would help them defy that history.

But stubbornly high 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.

Fears of rising crime were also a factor in left-leaning areas like New York, where incumbent Democratic Governor Kathy Hochul faced a tough challenge from Republican Lee Zeldin.

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"We have criminals constantly repeating crimes. They go to jail and come out a few hours later or the next day," said John Delsanto, 35, a legal assistant in New York City who said he voted for Zeldin.

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 block bills addressing 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.

READ MORE: US inflation rises more than expected

Republicans could also initiate a showdown over the nation's debt ceiling, which could shake financial markets, and launch investigations into Biden's administration and family.

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.

Inflation, abortion: voters' top concerns

Inflation and abortion led the list of issues identified by American voters as mattering most to their ballots in the 2022 US midterm elections, according to the NBC News Exit Poll released Tuesday evening.

The pool found that nearly one-third of voters named inflation and 27 percent named abortion when asked which issue mattered most this year.

Trailing these concerns were crime and gun policy – each named by 12 percent of voters, followed by immigration, which stood at 10 percent.

Across the country, Republican candidates have emphasized crime, inflation, and immigration as part of their campaign messaging.

Many Republican voters shared these concerns, the NBC poll showed, with 44 percent naming inflation as the most important issue, followed by immigration.

By contrast, Democrats were overwhelmingly concerned about abortion, with 46 percent naming it as the most important issue, followed by inflation and gun policy.