Democrat Joe Biden insisted Wednesday he will tackle coronavirus from Day 1 if he is elected president but warned there is no magic "switch" that ends the pandemic, as Donald Trump campaigned across America seemingly unfazed by Covid-19's dangers.
Six days before a momentous US election, Biden cast his presidential ballot in his home state of Delaware and met with health experts as he fine-tuned his pandemic response plan, seeking to reassure voters that he would use science to fight the contagion.
"Even if I win it's going to take a lot of hard work to end this pandemic," the former vice president said in Wilmington.
"I'm not running on a false promise of being able to end this pandemic by flipping a switch," he added. "But what I can promise you is this: we'll start on Day 1 by doing the right thing. We'll let science guide our decisions."
As Biden, 77, campaigns cautiously, holding low-key events with small socially-distanced crowds, the President was making final pitches to voters in battleground states that he desperately needs to secure four more years in office.
The pandemic has upended all aspects of American life and overshadowed the election, with polls showing it may well be the President's undoing as cases hit record levels in the US.
With many Americans fearing the risk of voting in crowded polling stations, a remarkable 74.7 million people have already cast their ballots.
After rallying supporters in three states Tuesday, Trump overnighted in a fourth, Nevada, ahead of back-to-back Arizona rallies Wednesday as he continued a breakneck pace.
With the glaring contrast in campaign styles evident days before an election both sides describe as the most important of their lifetimes, Biden's team announced that ex-president Barack Obama will join his former righthand man on the campaign trail in key state Michigan.
It will be their first joint in-person appearance of the 2020 race, and Obama will no doubt repeat his searing attacks on Trump's handling of the virus.
Some 57.4 per cent of Americans disapprove of Trump's coronavirus response, while 39.8 per cent approve, according to a poll average compiled by tracker FiveThirtyEight.com.
By contrast, a RealClearPolitics average shows 50 per cent approve of Trump's handling of the economy while 47.8 disapprove.
As polls show Biden leading in the final week, the 77-year-old has gone on electoral offense as he seeks to expand his state-by-state path to victory in the November 3 vote.
On Tuesday Biden visited Georgia, traditionally Republican territory, and he has said he would travel to Florida, Wisconsin and Michigan in the race's closing days.
All are states that Trump won in 2016 but which are up for grabs this year.
Trump, who at 74 caught and overcame Covid-19, is throwing coronavirus caution to the wind.
He hosted massive rallies before mostly mask-less crowds Tuesday in Michigan and Wisconsin and then in Nebraska, where he was hunting for a single Electoral College vote, a sign of how Trump's margin for error has narrowed.
In Lansing, Michigan, Trump stressed he was orchestrating an economic "super-recovery" while a Biden presidency would trigger a "depression."
But with American and European Covid-19 cases rising and no agreement yet on a new US pandemic rescue package in Congress, the Dow Jones on Wednesday sank three per cent by early afternoon, its fourth straight session of losses.
Trump has repeatedly stressed that the US is "rounding the turn" on the pandemic, but figures do not bear that out: more than 227,000 Americans have died and daily case averages have risen.
"All they talk about is Covid, Covid, Covid, Covid, Covid," Trump said at his Omaha rallty. "It's incredible. Excuse me. I'm here! Right?"
But his own chief infectious disease specialist, Anthony Fauci, offered a warning Wednesday.
Even if a Covid-19 vaccination comes on line this year, "it will be easily by the end of 2021, and perhaps even into the next year, before we start having some semblances of normality," he told a University of Melbourne panel.
Biden blasted the President, calling his administrations response to the pandemic "an insult to every single person suffering from Covid-19 and every family who's lost a loved one."
The White House said meanwhile that it was closely following the situation in Philadelphia, where a second straight night of unrest and looting has set the city on edge following the fatal police shooting of a Black man, the latest to spark anger in the United States.