That quintessential sound of an approaching election in Philadelphia — a sharp knock on your door — has fallen silent.

There are no volunteers on the steps with a stack of campaign literature — and, in the era of social distancing, packed rallies are out, too. Instead, hope your WiFi connection holds up while a politician asks for your vote in a Zoom meeting.

As they mourn the loss of the normal rituals of electioneering to the coronavirus pandemic, those who seek office or run campaigns in Pennsylvania say nobody has a clue how Tuesday’s primary election might go.

Even former Gov. Ed Rendell, always quick with political analysis or predictions, was at a loss.

“All I know is I already cast my vote via mail,” Rendell said.

More than 77% of the usual polling places in Philadelphia have been closed. More voters in the city have requested mail ballots than did across the whole state for the primary in 2016. Almost two million Pennsylvanians have requested to vote by mail.

And after several election cycles that saw an increase in political activism due to the national political scene, this primary really holds only one competitive statewide race, the Democratic battle for the relatively low-profile post of auditor general.

The Democratic race for president is over. Bernie Sanders is on the ballot Tuesday, but he has endorsed the presumptive nominee, Joe Biden. Several regional Democratic primaries for state House and Senate seats are competitive.

This time, the real drama is not who wins but how the election itself goes.

“I have no idea what’s going to happen,” said Bob Brady, chairman of Philadelphia’s Democratic City Committee. "No one does. We’re in completely strange and virgin territory.”

Brady, leader of the 34th Ward, said the uncertainty is compounded by the decision to compress polling places for safety. His ward in Overbrook usually has 42. On Tuesday it will have five. And the party volunteers who pass out sample ballots offering suggestions for voters will be missing in action.

“Anyone gets sick, it’s going to be crazy,” Brady said. “I’m telling my committee people, Don’t even come to the polls. What are you going to do? You can’t pass anything out.”

» READ MORE: From ‘Can I have your vote’? to ‘How can I help?’ Coronavirus transforms campaigning for the Pa. primary.

Other election day traditions are on hold as well. Politicians have gathered for decades at the Famous Fourth Street Deli, swapping the day’s gossip over enormous sandwiches and big bowls of matzo ball soup.

David Auspitz, the Queen Village eatery’s former owner, still coordinates the affair. But there will be no big lunch Tuesday.

“There’s literally nowhere to go for lunch,” joked Auspitz, who like other longtime political players wondered if the oddness of Tuesday’s election will stretch into the general election. “November is going to come pretty quick. We’ll be back together. I guess. I don’t know.”

U.S. Rep. Dwight Evans launched a competing lunch tradition 13 years ago at Relish, a restaurant in West Oak Lane, which draws governors, mayors, members of Congress, and others for a popular barbecue buffet. That too is off.

Evans said Tuesday will provide a “learning curve” to help plan for November.

“We will figure it out,” he said. “We’re not giving up. It’s just a question of how we are for the future. We’ve got five months to go. We’ve got some time to think about it.”

» FAQ: Your coronavirus questions, answered.

Finding a frame of reference is elusive. Political consultant Mark Nevins is helping manage Nina Ahmad’s bid in the Democratic primary for state auditor general. He noted Tuesday’s election is already “unfamiliar territory” because the state for the first time allows people to vote by mail without providing an excuse, unlike for absentee ballots in the past.

“Political planning usually involves examining past performances to predict future results,” Nevins said. “But there are no models that help us predict the impact of a once-in-a-century global pandemic on voter behavior.”

Like others interviewed for this story, Nevins said anyone claiming to know with certainty how the election will play out “is really just guessing.”

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

Philadelphia elections officials expect more than half the votes to be cast by mail. But it’s hard to know how many of the 220,000 or so voters who have requested ballots will actually return them on time for the election-night deadline, instead of voting in person or not at all. In the past, about one out of five voters who requested an absentee ballot ended up not using it.

Who ends up voting by mail, and how the pandemic might reshape the electorate, is also impossible to predict. Voters in low-income neighborhoods requested mail ballots at lower rates than even past turnout would suggest, and the voters requesting mail ballots are also older than the overall electorate. Voters over 60 years old have requested 36% of the city’s mail ballots while making up 27% of the active voters on the rolls. Voters under 30, meanwhile, make up about 16% of ballot requests but 21% of active voters.

Whether such gaps persist in the election overall, and whether the electorate looks different this time, will depend on how many of those mail ballots are returned and who ends up voting in person Tuesday.

Ahmad, a former deputy mayor in Philadelphia, is hoping the new reliance on technology to stay connected will engage younger voters in the process and expand the electorate.

“There’s a lot of different people using platforms to reach people,” she said. “Young people are very nimble on those platforms.”

Elliot Curson, a consultant who created media campaigns for Republicans in the city and once did Ronald Reagan’s ads, predicted a surge in voting from the mail-in option.

“It’s easy. You don’t have to do anything. Just fill out a form. Go online," Curson said. “I think people will be surprised by the number of people voting.”

Vince Fumo, a former state senator who represented South Philadelphia, does not expect the coronavirus to discourage many of his former constituents from going to polling places. He sees people visiting supermarkets and other open retail outlets as a sign of confidence.

“I don’t think there’s going to be a lot of fear of catching the virus from voting,” he said. “I don’t think the virus is going to affect it that much.”

Maurice Floyd, a political consultant and former city commissioner, is not so sure. He expects worries to continue into November.

“I don’t know if we’ll ever get back to normal,” he said. “I think people are still freaked out about what’s going on.”

And, even though there are few contested races on the ballot, actual confirmed election results will be hard to come by Tuesday night, due to the counting of mailed ballots that can’t start until the polls open.

» READ MORE: It could be a long wait for actual election results

Larry Ceisler, a media consultant who has run Democratic campaigns, sees an advantage in the pandemic for incumbents, who have name recognition and established fund-raising networks.

“You’re really depending here on social and digital media, with direct mail to a certain degree,” he said. “And if you can afford television advertising, then that’s great.”

Neil Oxman, a Democratic consultant and ad maker, is worried about the primary being a “bad precursor” to the November election. Among the scenarios troubling him: People accustomed to walking to polling places give up when they learn their place to vote has been relocated farther from their homes. He noted Republicans historically have had a stronger habit of regular voting than Democrats.

“This is going to be a gigantic thing in the general election all over the country,” he said. “And I think Democrats are screwed because it’s a bigger problem for us than Republicans. Enthusiasm means something. It is a thing. It’s real.”

Staff writer Jonathan Lai contributed to this article.