Voting is under way on Tuesday for the U.S. midterm elections, with Democrats fearing they could lose control of at least one of the two chambers in Congress amid high inflation and the dwindling popularity of President Joe Biden.

While the midterms usually serve as a referendum on the incumbent leader, Biden has sought to make the elections about his predecessor Donald Trump and "extremist" Republicans aligned with him, warning that they threaten democracy and basic rights, including through their denial of the results of the 2020 presidential race.

The election outcome will likely define the 79-year-old Biden's remaining two years in the White House and his potential re-election bid in 2024. It may also shape the political future of Trump, 76, who has actively rallied for Republican candidates in the midterm cycle and appears eager to run in the next presidential election.

Voters check in at a polling site in New York for the U.S. midterm elections on Nov. 8, 2022. (Kyodo)

In Tuesday's contests, all 435 seats in the House and about one-third of the 100 seats in the Senate are on the ballot. In addition, 36 out of 50 states will elect governors.

The Democratic Party currently holds a slim majority in the House. The Senate is evenly divided, but Democrats hold the majority due to the tie-breaking vote of Vice President Kamala Harris.

Polls have shown that Republicans are likely to gain a majority in the House. They are also slightly favored to win the Senate, election forecaster FiveThirtyEight said, with races in Georgia, Nevada and Pennsylvania expected to play a crucial role.

A Republican-controlled House could stall Biden's legislative agenda, ramp up oversight of the administration and launch congressional investigations into the president's son Hunter, who has been accused of engaging in shady business dealings in Ukraine and China.

On the diplomatic front, no substantive changes are expected in the current U.S. stance to pursue a tough China policy, due to bipartisan consensus on the issue. But the Biden administration's efforts to support Ukraine against Russia's invasion could be complicated as some Republicans have questioned the ballooning costs.

During the election campaign, Republican Party members criticized the Democratic administration for creating historically high inflation through what they view as "wasteful" government spending. They also accused Democrats of being soft on crime and illegal immigration.

A Supreme Court decision in June to eliminate the constitutional right to abortion lifted optimism among Democrats that the strong public backlash could help them defy the historical trend of the president's party losing House seats in midterm elections.

Over the summer, Biden also scored a series of legislative wins intended to lead to major investments and job creation in the country.

But with the economy and inflation remaining at the top of voter concerns, Republicans were seen regaining momentum in the weeks ahead of the elections.

According to Gallup polling data, presidents with an approval rating below 50 percent have seen their party lose an average of 37 House seats in the midterms.

The polling organization said in a report on Nov. 1 that Biden's 40 percent job approval rating was higher than only one other recent president at the time of midterm elections -- George W. Bush in 2006, at 38 percent.

More than 45 million people have voted by mail or taken advantage of early in-person voting ahead of election day, according to data from the University of Florida's U.S. Elections Project, surpassing the 39.1 million who did so in the last midterm elections in 2018.

This year's midterms are the first major election in the United States since a pro-Trump mob stormed the Capitol in January 2021 in an attempt to overturn the 2020 presidential election. Trump had called that election "rigged" and continues to repeat the claim without evidence.

The former Republican president, while facing questions over his role in the Capitol riot and criminal probes into his businesses and handling of classified documents, said during a recent rally that he will "very, very, very probably" run in 2024.

During his four years in office, Trump pushed ahead with his unilateralist "America First" foreign and trade policy, which has been criticized for undermining long-standing alliances, multilateralism and international organizations.

Biden, who became the oldest-ever U.S. president at the time of inauguration, said in a TV interview in October that it was his "intention" to throw his hat in the ring again, while acknowledging he had not made a formal decision.

Combined photo shows U.S. President Joe Biden (R, Getty/Kyodo) and former U.S. President Donald Trump (Getty/Kyodo). 

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