Joe Biden has made a long list of promises for his first 100 days if he is elected president, but his overriding priority would be the coronavirus pandemic.
In addition, he would try to roll back the political clock as much as possible to January 2017, when he and Barack Obama left office.
That would involve quickly signing executive orders to overturn ones signed by Donald Trump, including the travel ban on several mostly Muslim countries.
He has also pledged, on day one, to rejoin the Paris climate accord and to sign directives tightening environmental regulations that were loosened by Mr Trump.
Mr Biden would also prioritise international relations with a flurry of first day Oval Office calls to world leaders, reassuring allies about the US's role on the global stage.
Looming over his first 100 days would be a Supreme Court case, brought by the Trump administration and other Republicans, seeking the striking down of the Aff- ordable Care Act, known as Obamacare.
Arguments in the case are due to be heard next Tuesday, but a ruling is expected in the first half of next year.
If Obamacare is gutted by the court in his first 100 days, much of Mr Biden's energy could be taken up with that. He has vowed to respond by introducing a replacement called Bidencare.
With Republicans likely to hold on to the Senate, much of what he wants to do would be an uphill struggle.
On the pandemic, Mr Biden has indicated he would quickly issue a mandate for the wearing of masks on federal property and on all US "interstate transportation".
Mr Biden would also move quickly to appoint the cabinet secretaries key to the pandemic response. They include the health secretary, treasury secretary and the director of the National Economic Council.
He would also prioritise seeking advice from Dr Anthony Fauci, America's leading infectious diseases expert, and make him a pivotal figure in the response.
Dr Fauci has had a fractious relationship with Mr Trump, but is trusted by a high proportion of Americans.
Mr Biden would also quickly appoint a "supply commander", giving them responsibility for producing and distributing tests, masks and vaccines.
His plans include a new "pandemic board" that would decide what resources were required.
On his first day in the Oval Office, he would "restore our leadership on the world stage" by taking actions including a reversal of Mr Trump's withdrawal from the World Health Organisation.
Mr Biden would also move quickly to host a climate conference of many nations.
"The first thing I'd do as president is call a meeting of all the nations who sign on to the Paris accord, in Washington DC, to up the ante," he said.
"We've learned so much just in the last years about the science, about what has to happen quicker."
Mr Biden has vowed to take immediate action to reverse tax cuts, for individuals and companies, that Mr Trump secured in 2017.
In the first 100 days a new police oversight body would be set up to address institutional racism.
A bill would be sent to Congress to end gun background check loopholes.
In the final presidential debate, Mr Biden also said: "Within 100 days I'm going to send to the United States Congress a pathway to citizenship for over 11 million undocumented people."
Another immediate step would be setting up a federal task force to reunite around 500 children separated from their parents at the US-Mexico border under Mr Trump.