Pennsylvanians are voting Tuesday in an atmosphere with few precedents — if any.

On top of a pandemic that had already scrambled elections across the country, the vote will come after days of protests over the killing of George Floyd as Minneapolis police knelt on his neck and violent clashes that have added more tension — and left an already stricken Philadelphia smoldering in places.

The Democratic presidential primary is effectively over, so the biggest test may be for election officials. How people vote may be as important as who they vote for.

Pennsylvania will be holding its first statewide election since the onset of the coronavirus, and officials were already facing huge challenges amid social distancing, short-staffing, and a flood of requests for mail ballots far beyond anything Pennsylvania has ever seen — before protests and looting.

And there was even a last-minute twist: Gov. Tom Wolf on Monday extended the deadline for receiving mail ballots in Philadelphia, Pittsburgh, and a handful of other counties.

Even with that change, could Tuesday produce another Wisconsin, where voters in April were forced to stand in long lines and thousands of ballots didn’t reach voters in time? How long will it take to get results? And is there anything the outcome can tell us about the state of play in a swing state critical to the presidential election?

» READ MORE: Live coverage of what's happening Tuesday, Pennsylvania’s primary day

Here’s what we’ll be watching:

Will it be chaos?

Put simply: Will people be able to safely and efficiently exercise one of their fundamental rights?

Even before the coronavirus and civil unrest, this was likely to be a challenging election for Pennsylvania. It’s the first since a change in state law allowed anyone to request a mail ballot for any reason.

So officials were preparing for a surge in mail-in ballots, but the coronavirus put that into overdrive. About two million people had applied for mail ballots as of late last week, up from 107,000 for the state’s 2016 primary.

Voting by mail gave voters another option for avoiding crowds, but it also meant a heavy lift for election officials left short-handed by the virus. They’ve been struggling to process the requests, and to staff polling sites for people who choose to vote in person.

Some places have dramatically reduced polling places, including by 60% in Montgomery County and 77% in Philadelphia. That could create long lines and confusion.

If it’s harder to vote in certain counties, that could also have significant political implications in November, since geography and party affiliation are closely linked. Some counties face greater staffing shortages than others. Some sent out mail-in ballot applications to voters, while others required people to request one.

» READ MORE: Philly will have mail ballot drop boxes for voters today. Find yours here.

At least the primary will give officials a chance to see the challenges before November’s general election, when the presidency may hinge on how Pennsylvania votes.

The mail race

With the coronavirus a potential factor again in the fall general election, both parties have emphasized vote-by-mail in the primary, hoping to get supporters accustomed to it.

Except for President Donald Trump. Despite using mail-in ballots himself, and the established rarity of voter fraud, the president has falsely attacked them as prone to fraud. That has discouraged some Republican voters from using mail voting, even as the national and state GOP promote it.

» READ MORE: Pennsylvania Republicans don’t want to vote by mail: ‘We’re listening to Trump on this’

As of late last week, almost 1.3 million Democrats had been approved for mail-in ballots, compared with about 529,000 Republicans.

So will Republicans instead turn out in person in big numbers? Or has Trump depressed turnout within his own party?

And which regions and demographics will show up? In Philadelphia, voters in low-income neighborhoods requested mail ballots at disproportionately low rates. Who will vote by mail, who votes in person, and who, in the face of a public health threat, won’t vote at all?

Both sides see the primary as a test run for November, so even a small imbalance in who votes could be significant in a state decided by less than one percentage point in 2016.

“In some ways voting is like exercise, if you’re used to doing it you do it more and if you don’t it’s really hard to do,” said J.J. Balaban, a Democratic strategist in Philadelphia. “People in Pennsylvania are used to voting a certain way and now we’re getting to vote in an entirely different way.”

» READ MORE: The top races to watch in Tuesday’s Pennsylvania primary

How many people won’t get their ballots in on time?

Before Wolf’s election-eve order, it looked likely that thousands or even tens of thousands of voters wouldn’t receive their mail ballots in time to return them, threatening to disenfranchise them — or forcing them to face the health risks of voting in person.

Now, mail ballots still have to be postmarked by Tuesday, but in Philadelphia, Delaware, Montgomery, Allegheny, Dauphin, and Erie Counties, they will be counted if they are received by election officials by 8 p.m. June 9, a week from the original deadline. But the pandemic has slowed the process and some counties expected that some voters wouldn’t receive their ballots until Monday or even Tuesday. That could still make it difficult for those voters to mail ballots back in time.

Counties have scrambled to set up drop boxes for voters to hand-deliver ballots, and mail voters can instead use a provisional ballot at polling places. But not everyone is willing or able to do so.

Will people get sick?

Lines of voters. Shared voting machines. Poll workers interacting with hundreds of people.

All of it adds up to the possibility some people could become sick from voting in person, and officials are scrambling to provide personal protective equipment and cleaning supplies.

Voters and poll workers in other states have contracted the coronavirus, and a poll worker in Chicago died of COVID-19 15 days after a primary there in March.

When will we get results?

Be prepared to wait for results.

Elections officials had already said for months that counting votes would take much longer with the increase in mail ballots.

Many counties had planned to begin counting mail ballots on election day but didn’t expect to finish until at least the next day. Some weren’t even planning to start until the day after the election. And after Wolf’s order, several counties could still be counting many votes for a week or longer.

» READ MORE: Want to know who won the presidential race on election night? Get ready to wait.

The process will give us the first look at what could be an even more agonizing wait in in November, with higher turnout and greater stakes.

2020 tea leaves

It’s risky to extrapolate from primaries, which draw different electorates than general elections.

Normally, we’d examine Tuesday’s results for signs of strength and weakness for Trump and presumptive Democratic nominee Joe Biden. Can Biden draw white Democrats who fled to Trump in 2016? African American voters in Philadelphia? Progressives? Can Trump produce another surge of rural enthusiasm?

But those questions are tough to answer now. Political strategists in both parties said they’ll be looking — maybe — for which party does better getting their supporters to vote in difficult circumstances.

After that? Interpret at your own risk.

“Primaries are not usually very good indicators of general election performance,” said Mark Harris, a Republican strategist from Pittsburgh. “How willing people are to vote by mail might be an interesting thing.”

“I would be really skeptical about drawing a conclusion,” one Pennsylvania Democratic operative said. “I just think the data is going to be so influenced by external events it’ll be hard to tell what’s real and what’s not.”