The coronavirus pandemic has already caused immeasurable disruption around the world, shutting down national economies and forcing millions of people to change the way they live their lives.
Come November, it could disrupt the most important political event of the year – the US presidential election.
The election is scheduled for November 3. It will happen on that date, whatever the status of America's fight against the virus.
Perhaps the threat will have passed by then, and the country will be back to normal. But it is entirely possible Americans will still be operating under some form of lockdown or social distancing.
If that's the case, how exactly are they supposed to cast their votes?
That question, and the potential answer to it, have sparked a fierce debate. Democrats are pushing to prepare for an election conducted largely by mail. Republicans, among them President Donald Trump, are resisting.
AN ALREADY FLAWED SYSTEM
Voting in America is already unnecessarily difficult, even at the best of times.
Bafflingly, the election is always held on a Tuesday. That tradition has its origins in the 1800s, when people's weekly routines were rather different.
The idea was to give farmers enough time to make it to their county seats, without impinging on times of worship or market days.
Now, the Tuesday tradition means people either have to take time off work to vote or try to cast their ballot in the early morning or late evening.
This leads to people standing in line for hours. During the Democratic primaries earlier this year, for example – back when they were still competitive – there were reports of people waiting five or six hours at some polling places.
Then you take into account considerations like childcare. If you are a single parent working a full-time job, you do not have a couple of spare hours to spend voting.
The result of all this is a nation with abysmal voter turnout.
Fewer than 60 per cent of Americans cast ballots in 2016. So when you see the official popular vote for that election, with Hillary Clinton earning 48.2 per cent and Mr Trump 46.1 per cent, it's actually a little deceptive.
In truth, both candidates only earned the support of about 27 per cent of the eligible voting population. Mr Trump was elected President by just a quarter of the country.
That is the baseline here. Many Americans already found it too hard to vote, and the virus could make it harder – restricting the democratic process to an even narrower slice of eligible voters than usual.
'THE NIGHTMARE SCENARIO'
The danger is that voters will face a choice between going to the polls and potentially exposing themselves to the virus, or staying home and missing out.
"The prospect that terrifies election experts isn't the idea that Trump moves the election," Politico wrote this week.
"It's something altogether more plausible – despite an ongoing pandemic, the 2020 election takes place as planned, and America is totally unprepared.
"The nightmare scenario goes something like this. Large numbers of voters become disenfranchised because they're worried it is not safe to vote, and that participating makes it more likely they will catch the coronavirus."
That's the problem. Democrats think they have the solution – mail-in voting. But even that presents some worrying challenges.
At the moment, the rules around voting by mail are a complicated patchwork, with each of America's 50 states using its own system.
Five states – Colorado, Oregon, Washington, Utah and Hawaii – already send mail ballots to everyone, even in normal times.
Twenty-eight states allow residents to vote by mail for any reason, but require them to actively request a mail ballot.
Among this group are a number of the crucial swing states that will decide the election – Florida, Pennsylvania, Ohio, Michigan, Wisconsin, Arizona and North Carolina.
Then there is the last group. Seventeen states only grant voters absentee ballots for specific reasons, and while "illness" is generally one of them, it is unclear whether fear of catching the coronavirus would be enough to qualify. The most significant example here is Texas, the second-largest state in the country.
In these states, voters could conceivably be forced into that nightmarish choice between risking exposure to the virus and forgoing voting altogether.
'IT'S CORRUPT': TRUMP SOWS DOUBT
Democrats in Congress want the US to prepare for the scenario outlined above. They have suggested sending mail ballots to everyone, or tweaking the rules in every state to allow anyone to vote by mail, even without the usual justification.
But to get either of those measures through Congress, they require the support of the Republican Senate. And it is not forthcoming.
Mr Trump is vehemently opposed to expanding access to mail voting. He argues it would lead to widespread voter fraud.
"Mail ballots, they cheat. Mail ballots are very dangerous for this country because of cheaters. They go collect them. They are fraudulent in many places," Mr Trump said during one of his coronavirus briefings at the White House on April 7.
"I think mail-in voting is horrible. It's corrupt."
One reporter pointed out that Mr Trump himself had utilised mail voting in the past. That didn't shift the President's opposition.
"But you voted by mail in Florida's election last month, didn't you?" the reporter asked.
"Sure, I can vote by mail," Mr Trump said.
"How do you reconcile that?" the reporter pressed.
"Because I'm allowed to," the President replied.
"I happen to be in the White House, and I won't be able to go to Florida to vote."
Mr Trump has made wild claims about voter fraud before without any evidence to back up his views, but this time he is exaggerating a real problem.
The Massachusetts Institute of Technology has studied the issue in some depth, and has found mail voting is more vulnerable to fraud than in-person voting.
"There are two major features of (absentee voting) that raise these concerns. First, the ballot is cast outside the public eye, and thus the opportunities for coercion and voter impersonation are greater," MIT said.
"Second, the transmission path of ballots is not as secure as traditional in-person ballots. These concerns relate both to ballots being intercepted and ballots being requested without the voter's permission.
"As with all forms of voter fraud, documented instances of fraud related to mail voting are rare. However, even many scholars who argue that fraud is generally rare agree that fraud with mail voting seems to be more frequent than with in-person voting."
There are other practical problems as well.
The US Postal Service may not be equipped to deal with the drastic increase in volume that a large mail-voting effort would inevitably cause. The Trump administration has yet to approve a $US10 billion loan to the service, which was proposed during the process of passing America's coronavirus stimulus measures.
Absentee ballots take longer to count on election night, which means a large shift towards them and away from in-person voting could leave the country without an immediate result. This, too, was mentioned as part of Politico's hypothetical "nightmare scenario".
"A flood of mailed-in ballots makes it impossible to get full returns on election night, with heavily blue Democratic cities being, as usual, among the slowest to count," it wrote.
"Trump declares victory based on those early returns on election night, and again claims that the yet-to-be-counted absentees are tainted with fraud. Days later, with those votes counted, Joe Biden is declared the victor.
"Across the political spectrum, faith in the democratic process disintegrates as Americans question the validity of the election."
It's a plausible scenario.
Finally, there is the risk that too many mailed-in votes won't be counted at all.
Under the existing rules, absentee ballots are rejected for all sorts of reasons. They might not arrive in time due to postal delays. The envelope might be missing one required piece of information, like a driver's licence number.
A survey of the 2018 midterm elections found 8.2 per cent of absentee ballots were not counted. That isn't a huge number under normal circumstances. But if a majority of people decide to vote by mail this year, we're suddenly talking about millions of votes being disqualified – and that is even if the postal system is able to cope.
The election between Mr Trump and Ms Clinton was ultimately decided by a few tens of thousands of votes, spread across three critical swing states.
The 2000 election between George W. Bush and Al Gore infamously came down to a few hundred ballots in Florida.
If the virus is still around in November, and mail voting becomes essential, any administrative slip-up could prove disastrous.
CAN'T TRUMP JUST DELAY THE ELECTION?
Finally, you may be wondering whether Mr Trump has the power to postpone the election until the virus is no longer a concern, sidestepping the problem altogether. The answer to that question is a firm no.
The US Constitution gives Congress, not the President, the power to set a date for the presidential election. For that date to change, the House of Representatives and the Senate would both need to pass a piece of legislation – and they haven't been agreeing on much lately.
Speaking to MSNBC this week, prominent Democratic Senator Adam Schiff was asked whether he was worried that Mr Trump might try to delay the election.
"I'm more worried he will try to disenfranchise millions of Americans than that he will try to put off the election," Mr Schiff said.
"He's already talking down absentee voting, making false claims about the reliability of absentee voting, even when he votes by absentee himself.
"The Republicans may try to force people to choose their vote or their health. And we need to insist that every American, if they choose to do so, has easy access to voting by mail."
His words made it clear that a delayed election remained an extremely remote possibility. In all likelihood, polling day will go ahead as planned on November 3.
We have no idea whether the US is actually ready for it.