The coronavirus pandemic has taken a wrecking ball to the Olympics, Edinburgh Festival and UN’s Cop26 climate conference. In America, presidential primary elections have gone down like skittles, the Democratic national convention has been postponed and campaigns are frozen in time.

All of which raises the question: can the 2020 general election itself survive?

The presidential vote is due to take place on 3 November. The date is set by federal law and Donald Trump has no power to delay it alone. That would require legislation enacted by Congress and signed by the president. Such an outcome still remains unthinkable to most. But many unthinkable events have unfolded in the last month.

“We’re in completely uncharted waters here and I don’t think anybody knows what’s going to happen,” said Monika McDermott, a political science professor at Fordham University in New York. “By November the picture might be completely unrecognisable. We don’t even know if the election is going to happen as scheduled. There’s talk out there about postponing it or changing it to a mail-in only election.”

The profound uncertainty has upended political campaigns like nothing else in living memory. It was a month ago – 3 March – that the former vice-president Joe Biden won 10 states on Super Tuesday, the biggest day in the primary calendar, and took firm control of the Democratic race. Trump, meanwhile, was holding regular campaign rallies in packed arenas.

Now, Biden finds himself holed up in his basement in Wilmington, Delaware, struggling to break into the national conversation through TV interviews and virtual campaign events. Trump has been denied the lifeblood of rallies but switched to his other favourite medium – television – with daily coronavirus taskforce briefings from the White House. Polls suggest he is benefiting moderately from a “rally around the flag effect”.

Media coverage that would normally be all about the race for the White House is dominated instead by an extraordinary public health and economic crisis, with the US death toll from the virus expected to top 100,000. Trump and Biden continue to work on the assumption that, come November, the worst of the pandemic will be over. The US held midterm elections in 1918 even in the grip of the Spanish flu that killed 675,000 people nationwide.

Joe Biden speaks about the coronavirus pandemic in Wilmington, Delaware, on 12 March. Photograph: Carlos Barría/Reuters

Fifteen states and one territory have postponed their primaries already this year, denying Biden the chance to knock out his rival, the Vermont senator Bernie Sanders, sooner rather than later. But Wisconsin intends to go ahead next week, despite legal challenges, an objection from Sanders and shortages of poll workers that could force the national guard to step in.

June will now be a bumper month, with nearly 700 delegates up for grabs in 10 states and the District of Columbia on 2 June alone – assuming the primaries can go ahead. On Thursday the Democratic National Committee announcing it was delaying its presidential nominating convention in Milwaukee by a month until the week of 17 August.

But changing general election day would be much more difficult. Faced with the inconsistency of states voting on different dates, Congress passed a law in 1845 that stipulated federal elections must be held on the Tuesday after the first Monday in November (the day and time of year were chosen to suit farmers).

Congress would have to pass a new law to postpone the 2020 election and even then would run into constitutional hurdles stating the new Congress must be sworn in on 3 January and the new president’s term must begin on 20 January.

The inauguration date was set in 1933 when the 20th amendment to the constitution was ratified. There have only been 27 amendments in all. To make another, revising the inauguration date, would require approval by a two-thirds majority of both the House of Representatives and Senate, then ratification by three-quarters of the states.

If the election does go ahead as expected on 3 November, states that already allow early and absentee voting will be well placed. Washington state, for example, has carried out elections by mail for years and its primary last month went ahead as planned. But 17 states require some kind of excuse for requesting an absentee ballot. Many would need to change their rules at huge cost to run a mail-only election.

Robert P Jones, founder and chief executive of the Public Religion Research Institute (PRRI), said: “There is a patchwork of state constitutions. The west coast is ahead of the curve whereas other states might have to scramble. One challenge is the United States postal service is economically unstable, so vote by mail may not be as simple as it seems right now.”

Such logistical problems could fuel concerns over the result in what is expected to be another very close election, Jones added. “We could end up with concerns about the legitimacy of the election. Last time it was only 10,000 votes in Michigan. It’s not hard to think we might have votes misdirected or ‘return to sender’.”

Bernie Sanders walks near the Senate chamber during the coronavirus relief bill at Capitol Hill in Washington DC on 25 March. Photograph: Erik S Lesser/EPA

Party politics are already a factor. Democrats sought $2bn in funding for absentee and vote-by-mail options in the recent coronavirus emergency relief bill but only got $400m. Trump admitted on Fox News: “The things they had in there were crazy. They had things – levels of voting that, if you ever agreed to it, you’d never have a Republican elected in this country again.”

At Friday’s White House coronavirus taskforce briefing he elaborated by claiming without evidence: “I think a lot of people cheat with mail-in voting. I think people should vote with ID – voter ID. I think voter ID is very important and the reason they don’t want voter ID is because they intend to cheat.

“It shouldn’t be mail-in voting. It should be: you go to a booth and you proudly display yourself. You don’t send it in the mail where people pick up – all sorts of bad things can happen by the time they signed that, if they signed that by the time it gets in and is tabulated.”

Republicans have long stoked fears of fraud in mail-in voting. But according to the Washington Post, in Washington state’s last election, 4.4m ballots were cast but fewer than a hundred were flagged and none led to a criminal fraud investigation.

What remains unknown is whether the pandemic will help or hurt Trump at the ballot box. He declared a national emergency on 13 March but has been fiercely condemned for previously downplaying the virus, squandering crucial weeks and leaving the country unprepared. The president has “has blood on his hands”, argued the Boston Globe editorial board this week, while Biden’s supporters say the former vice-president would bring precisely the stable leadership the country needs.

The PRRI says that, in less than three weeks, Trump has seen the highest increase in his favourability rating since the institute began tracking it in 2015. Its analysis of 1,008 adults polled between 17 and 22 March found that overall Trump’s favorability increased from 40% in February to 49% in March, with unfavorable opinion decreasing 10 points. Favourability in the battleground states of Arizona, Florida, Michigan, North Carolina, Pennsylvania and Wisconsin jumped 13 points.

Jones explained: “We’re seeing a typical American reaction at times of national crisis, a ‘rally around the flag effect’. It happened with George W Bush after 9/11 and Barack Obama after the killing of Osama bin Laden. But on this one, we’re looking at something different, the very front edge of the US finally taking this seriously.

Trump is getting points for showing up; he was largely absent in January and February Robert P Jones

“That’s what we’re registering: people saying he’s stepping up and taking it seriously after months of playing it down. Trump is getting points for showing up; he was largely absent in January and February. The real test will be: what will it look like a month from now?”

Robert Griffin, research director of the Democracy Fund Voter Study Group, agreed that the “rally around the flag effect” is benefiting the president but noted that, after the September 11, 2001 terrorist attacks, it was not only Bush but also state governors who saw a rise in their approval ratings.

“The effect is not necessarily related to performance or what the government is doing,” he said. “By historical standards, the effect for Trump is smaller than you’d expect and smaller than we’ve seen for other world leaders. His approval rating has not really changed that much and, for the 2020 election, it’s not moved the needle at all.”

Trump’s central re-election argument was the economy, but the coronavirus outbreak has caused the quickest collapse the US job market has ever seen, throwing 10 million people out of work in just two weeks, and destroyed countless businesses. Griffin said: “Economic shocks in an election year are about as bad as it could get in terms of timing for a president seeking re-election. How are the American people going to interpret the action of this administration?”

Trump’s critics believe that, pandemic or no pandemic, he was always doomed to defeat. Elaine Kamarck, a senior fellow at the Brookings Institution thinktank in Washington, said: “Trump was in trouble and I still think he is. As the autopsies go down on his handling of this, it’s not a good story.

“Trump does not have discipline and that has been the case all through his presidency. He does not take advice. He’s headstrong and he insists on what his gut tells him to do. He’s in a precarious position and I don’t think this pandemic changes it. If anything, it illustrates why he’s in that precarious position.”