With one week to go until the U.S. presidential election, Democratic challenger Joe Biden is maintaining a lead in national polls over Republican President Donald Trump who continues to face questions over his handling of the coronavirus pandemic.

Both candidates are making their final pitches in battleground states, seeking to cast themselves as a more viable leader to ride out the pandemic and its resulting economic setback as well as the recent flaring up of civil unrest over police brutality against black people.

Combined photo shows U.S. President Donald Trump (L) and Democratic presidential nominee Joe Biden participating in the presidential debate on Oct. 22, 2020, in Nashville, Tennessee. (Getty/Kyodo)

Biden, the 77-year-old former vice president, is leading Trump by around 8 percentage points, according to an average of national polling data by poll tracking website Real Clear Politics. Biden's lead comes to an average of about 4 points in the top six battleground states, including Florida and Pennsylvania.

Nonetheless, Trump, 74, has been bullish about his own prospects, saying he feels even more enthusiasm from his supporters than in 2016, when he defied election forecasts and clinched a victory over then Democratic presidential nominee Hillary Clinton.

He has also been looking to score last-minute points that would shore up his base, such as by filling the Supreme Court vacancy created after the death of iconic liberal justice Ruth Bader Ginsburg last month.

The Republican-controlled Senate on Monday confirmed the lifetime appointment of Trump's Supreme Court justice nominee Amy Coney Barrett, solidifying a conservative majority on the nine-member bench that would decide on abortion rights, voting rights and other key issues.

Trump has also stepped up corruption allegations against the Biden family, citing recent tabloid reports suggesting Biden's son Hunter profited off the former vice president's influence in overseas dealings, based on emails allegedly obtained from a laptop that Hunter had supposedly dropped off at a repair shop in 2019.

But some major U.S. media have questioned the authenticity of the data. Facebook Inc. and Twitter Inc. also took steps to limit the spread of the story for reasons including the need to fact-check the claims.

The move has enraged Trump, who has already been clashing with mainstream news media for publishing what he calls "fake news" when coverage is not as positive as he would like.

Coronavirus cases, meanwhile, have again started to surge in the country, contradicting repeated statements by Trump -- who contracted the virus himself earlier this month -- that the country is "rounding the corner" of the pandemic.

The pandemic has added to the uncertainty around the election, prompting more voters to turn to mail-in ballots and early in-person voting to avoid going to crowded polling places on election day.

Experts say this may result in delays and legal challenges to vote counts.

In a U.S. presidential election, Americans vote in each of the 50 states and the District of Columbia. The candidate who wins the popular vote in a state secures that state's "electoral votes," which are allocated according to the state's population, usually in a winner-take-all manner.

The candidate who receives a majority of the electoral votes -- at least 270 of the 538 total -- wins the White House. Due to the Electoral College system, a candidate can still become the winner while losing the popular vote.

In the 2016 election, Trump secured 306 electoral votes although Clinton won the popular vote by a margin of 2.1 points, or nearly 3 million votes.

On Nov. 3 this year, all 435 seats in the Democratic-controlled House of Representatives and 35 of the 100 seats in the Senate will also be contested.

Trump has privately told donors at a recent fundraiser that it will be "very tough" for Republicans to retain their majority in the Senate, according to The Washington Post. Democrats need to win three Republican-held seats if Biden wins the presidency to claim Senate control.

If Trump is not re-elected, he will be the first one-term U.S. president since Republican George H.W. Bush, who was defeated in 1992 by Democrat Bill Clinton.

A losing presidential candidate typically concedes shortly after the outcome is known. However, Trump has refused to commit to a peaceful transfer of power if he is defeated, and has also insisted that the only way he could lose the election would be because it is "rigged" with mail-in voting, which he claims leads to voter fraud.

Concerns are growing over possible domestic unrest or violence triggered by voters who become upset with the election results.

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