Sixty-three million people have already cast ballots with just one week to go until the final day of voting in the United States presidential election, and Donald Trump and Joe Biden are crisscrossing the country in a final blitz to win the backing of the remaining undecided voters and turn out their supporters.

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Interactive page: X Factors in the U.S. Election

The polling suggests the race is tightening a little.

Here's what you might have missed over the past seven days.

The candidates have visited many of the same states while taking starkly different approaches to campaigning, but their paths did cross in Tennessee for the final debate of the election.

Snap polls indicated voters believed Biden had the better of the clash in Nashville, but a more respectful and measured tone from Trump than in the rancorous first debate meant most pundits saw it as a score draw unlikely to change many minds.

Debate: Trump and Biden turn down volume

Graphics: Biden wins snap debate polls

The Democrat has continued his practice of low-key, socially-distanced events in swing states, but as the number of new COVID-19 cases in the U.S. hit a single-day record last Friday and several members of Vice President Mike Pence's staff tested positive, Trump embarked on a hectic rally dash, visiting as many as three swing states per day.

The president's frantic schedule is a sign of the state of the race: He is being forced to defend areas he won in 2016 that he had previously been very confident of winning again.

And as Trump defends, Democrats are attacking.

The party is targeting a trifecta – control of Congress and the White House – and is ramping up efforts in Republican states with tight Senate races: Biden is due in Georgia on Tuesday and Kamala Harris will be in Texas on Friday.

Pennsylvania – the tipping point in 2020?

Florida – a vote-rich election battleground

Both Republicans and Democrats have spent a lot of time and money in Pennsylvania, the state of Biden's birth, battling for the 20 electoral votes that could determine the winner.

Another big hitter on the campaign trail over the past seven days has also been in the Keystone state – former President Barack Obama. He critiqued Trump's job performance there before heading to another potential tipping point – Florida.

Of the many uncertain factors in the election, one of the most difficult to gauge is the impact of the huge increase in early voting.

Almost 50 percent of the total votes in the 2016 election have already been cast, but exactly what this means for 2020 is unknown: Will there be a huge increase in turnout or are these people who, in pre-pandemic times, would have voted on election day? Have younger voters turned out for Biden or has Trump expanded his base?

Voting will be over in one week, but unless one candidate is decisively ahead in key states – like Florida or Pennsylvania – on November 3, the winner may not be known until days or weeks later.

Video: Wang Zengzheng and Zhou Tingyu

Script: John Goodrich

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