The vote counting rules in the contested states make it difficult to determine a winner

Unless polls suggesting a razor-thin margin between Vice President Kamala Harris and former President Trump are completely wrong — a possibility due to dizzying changes in the way voters cast their ballots, as well as a pandemic-triggered overhaul of the Election laws — Americans should plan to go to bed Tuesday night not knowing who won the White House.

Election experts argue that a delay in announcing the results, in part because of the patchwork of rules dictating how votes are counted, particularly in battleground states, is evidence of election counters' vigilance in accurately recording votes. But they also worry that any delay will increase many Americans' growing skepticism about the sanctity of the country's electoral process.

“People are used to turning on their television late on election night and seeing a winner roll across the screen,” said Jessica Levinson, an election law professor at Loyola Law School. “I think that’s largely a thing of the past. It’s hard to imagine how this could have happened in such a close race.”

She noted that voters' behavior has changed in how they cast their ballots, and that there are different rules for when mail-in ballots can be counted and late mail-in ballots that are postmarked on Election Day were accepted. But she also fears that in today's polarized climate, election officials doing their due diligence to properly count votes will be misinterpreted as an opportunity for fraud.

“Everyone knows what a photo finish is,” Levinson said. Expecting a clear result on election night “is like declaring victory before you can develop the film.” Or it's like declaring victory before you take the final lap, because honestly, that's what counts last round.”

Charles Stewart III, the director of the MIT Election Data and Science Lab, said it will ultimately come down to winning the race.

“In all of these states, part of the answer really depends on how close the election actually is,” he said. “I say that because all that really matters is whether the election is really close.”

As of Sunday, more than 76 million Americans have voted, either by absentee ballot or in-person early voting, according to a tracker from the University of Florida's Election Lab. Several states have reported record-breaking early returns, including two that could tip the balance in the presidential race — Georgia and North Carolina.

According to the Secretary of State, more than four million Georgians had cast their votes as of Friday. The number far exceeds the number of previous elections.

“Georgia voters know we’ve made it easier to vote. It’s really that simple,” Secretary of State Brad Raffensperger, who famously opposed Trump’s efforts to increase his vote total in Georgia in 2020, said in a statement.

Some states have changed their election rules due to the pandemic, including California, which now sends ballots by mail to every registered voter, or in the wake of the contentious 2020 election. These include some of the battleground states that will decide who is elected president. Additionally, some of these states have restrictions on receiving or counting mail-in ballots.

In 2020, then-President Trump spoke out against mail-in voting — historically an election practice favored by Republicans. The end result was that voters saw candidates who appeared to be in the lead after the polls closed on Election Day and then lost after all the votes were counted. This led to widespread and false conspiracy theories about fluctuating vote counts in states like Michigan.

If Tuesday's election is similarly close, this scenario is likely to repeat itself.

“If the race comes down to a few thousand ballots in a key state, it could be days or weeks before we know the winner of the presidential election,” said Rachel Orey, director of the Bipartisan Policy Center’s Elections Project. “It really comes down to the profit margin.”

Rick Hasen, a professor of campaign finance law at UCLA whose latest book is “A Real Right to Vote: How a Constitutional Amendment Can Safeguard American Democracy,” said the rules in Pennsylvania, Wisconsin, Nevada and Arizona could hinder the declaration of a winner in a particularly close election.

“If it comes down to these states, there could be a delay of a few days for a variety of reasons,” Hasen said. “Pennsylvania and Wisconsin do not allow absentee ballots to be processed before Election Day. Wisconsin is developing faster because it is smaller, but the bottleneck is Milwaukee.”

“Nevada is a different problem, where ballots can arrive within four days” if they are postmarked on Election Day, he said. “And in Arizona there are just a lot of mail-in ballots, and it takes a long time, like in California.”

Another complication in Arizona is that voters in Maricopa County, the state's most populous, are being asked to complete the longest ballot in nearly two decades, Orey said. This could cause delays at voting centers as voters take longer to cast their ballots, slow down tabulation, and potentially cause paper jams in the counting machines because the ballot is two pages long, front and back

However, there are bright spots in other key states, he said. Georgia and North Carolina are counting votes relatively quickly, and Michigan has changed its rules and is expected to be faster than four years ago.

A key question is whether the election depends on a small number of votes in a state, as was the case in the race between Al Gore and George W. Bush in 2000.

“If it comes down to a few hundred or a few thousand votes in one state, it could drag on for weeks,” Hasen said, noting the chances of a repeat of this highly contentious election, which was ultimately decided by the Supreme Court , are small but not impossible. “Then all bets are off… It will be a turf war from ballot to ballot.”

Stewart added that both Harris and Trump's campaign had prepared for this possibility.

“They are as strong as a bear, as they say,” he said. “Hundreds of lawyers and hundreds of briefs are ready to go.”

Hasen's advice to worried voters: After polls close Tuesday, recognize that delays in reporting results are a sign that the system is working and remain calm.

On Tuesday night, “everyone needs to take a breath, have some patience, have a glass of wine and get up the next day and do it all again,” he said. “Maybe we’ll know what the answer is by the end of the week. Unless it’s a glitch.”