2020 déjà vu: Why the 2024 election could take days to call

• And in those toss-up states — Wisconsin, Arizona, Nevada, Michigan, Pennsylvania and Georgia — the margins in the race for president could be even closer this time.

Driving the news: Experts warn that most swing states' vote counting and certification procedures could again extend beyond Election Day, despite a mixed bag of rule changes.

• "It is a near guarantee that Donald Trump will declare victory the night of Nov. 5 and the margin won't matter — it won't matter whether he's accurate and he actually won, or whether he was defeated soundly," David Becker, executive director of the Center for Election Innovation and Research, told Axios.
• "I think we should absolutely expect that super-spreaders of disinformation will parrot the lies about the election in the immediate aftermath."

Zoom in: Trump calls voting by mail "corrupt" but has increasingly encouraged his GOP allies to take advantage of it, if necessary. He repeatedly has dodged questions about whether he'll accept the 2024 election results if he loses.

• He's threatened to seek to imprison anyone who engages in "unscrupulous" election behavior and warned law enforcement to "watch for voter fraud."
• Trump's campaign and allies say they've recruited roughly 175,000 poll workers and poll watchers, an effort that Democrats worry may lead to voter intimidation.

Flashback: Republicans' questioning of the integrity of elections ramped up before November 2020, when the pandemic led to more mail-in and absentee voting.

• "Sowing doubt ... is not enough to get the election overturned," election law expert Rick Hasen said.
• But "it's enough to create the conditions where people are more willing to do radical things to try to overturn the results, because they are more apt to believe that the election is being stolen." (No evidence of significant voter fraud has been found related to the 2020 election.)

In 2020, early returns showed Trump ahead, but as more votes were processed, Joe Biden's victory took shape. On election night Trump declared victory in states such as Georgia (which he ultimately lost), saying, "They can't catch us."

• Experts had predicted this, especially given Democrats' embrace of mail-in voting.
• Some call it the "blue shift": when Election Day results favor Republicans, but absentee and mail-in ballots counted later heavily favor Democrats.

Reality check: The MIT Election Data and Science Lab found that the pattern of results in 2020 wasn't much of an anomaly from 2016, and that the share of votes counted after Election Day was similar in both elections.

• The difference, however, was the "willful misrepresentation of the patterns" in certain key states, researchers wrote.

What they're saying: Trump's team is "dedicated to protecting every legal vote, mitigating threats to the voting process, and securing the election," Claire Zunk, the Republican National Committee's elections integrity communications director, said in a statement.

• Zunk accused Democrats of "election interference" and said the RNC is "prepared to litigate and ensure the election is fair, transparent, legal and accurate."

What has — and hasn't — changed

Arizona's drawn-out process is unchanged from 2020. The process of verifying signatures on early ballots that are dropped off on Election Day causes notoriously long delays in finalizing results.

• That means leads in close races could change as those ballots are counted in the days after the election.
• Maricopa County, home to more than 60% of Arizona's population, hired more temporary workers in 2022 to verify signatures, but it still took a week to call the close governor's race. They've added workers this year.

In Pennsylvania, county officials are sounding the alarm that counting again will probably take days. The state doesn't allow offices to begin opening mail-in ballots until 7am on Election Day.

• The process took days in 2020, and its divided state legislature has not agreed on major changes since.
• Plus: Several mail-in ballot rules are still being challenged in court.

In Wisconsin, a bipartisan effort that would have allowed election officials to begin processing absentee ballots before Election Day failed to pass the legislature this year.

• "We are sure to see the 'red mirage' and the 'blue wave' once again in 2024, where the early tally is likely to favor the Republicans, and then the absentees, cast largely by Democrats, are going to come in after that," UW-La Crosse political science professor Anthony Chergosky told Axios.

Nevada, Michigan and Georgia have, meanwhile, moved up vote-counting timelines.

• But 2024 will be their first presidential-level test — and in Georgia, officials warn that other political dynamics could blunt any newfound speed.

In Georgia in 2021, Republican lawmakers made several changes to counting rules, including moving up certification deadlines and requiring counties to continuously tabulate until 5pm the day after the election.

• Yes, but: That may be undermined by last-minute rules proposed by the conservative-controlled State Election Board.
• GOP Secretary of State Brad Raffensperger (who was removed from the board by the Legislature) told Axios the body is a "mess." He's worried the proposals weaken the chain of ballot custody and could delay results.
• "Quick results give voters confidence. Confidence builds trust, and trust is society's gold standard, particularly when our society is so polarized," he said.

In Michigan, officials are optimistic about faster results in 2024 — though this will be their first high-profile trial. After Democrats took control in 2023, lawmakers passed rules to allow absentee ballot counting up to eight days before the election.

• Michael Siegrist, Canton Township's clerk, tells Axios the change will mean a "sizable shift in how we report results on election night."
• He expects to have about 90% of absentee ballots counted before Election Day and unofficial results a few hours after polls close: "I don't envision a world where we don't know who won Michigan by midnight."
• Flashback: The state's August primary largely saw races called the night of the election, but there were few hotly contested campaigns.

In Nevada, clerks can this year begin tabulating early vote ballots when polls open, rather than when they close on Election Day. They can begin tabulating mail ballots on Oct. 21, per the Secretary of State office.

• Democratic Secretary of State Francisco Aguilar said in May the policy from his office should yield quicker results, which "will increase transparency, help us combat misinformation and alleviate pressure on election officials."
• Yes, but: Ballots postmarked before Election Day and arriving up to four days afterward will still be counted — meaning the timeline in some ways is out of officials' control.
• Flashback: The state's June primary saw quicker results than previous cycles, though turnout was lower.

What we're watching: Nationwide, both parties are more prepared for a litigious election season than four years ago.

• "Pre-election litigation has been pretty heavy," which could set the stage for more post-election challenges, said Benjamin Ginsberg, a Republican election lawyer.
• Republicans have filed more than 100 lawsuits against various 2024 election procedures, per the Associated Press.
• Vice President Kamala Harris' campaign told the New York Times its election legal team is 10 times larger than Biden's was in 2020.

Go deeper: America braces for perfect storm of election chaos

Axios' Thomas Wheatley, Isaac Avilucea and Joe Guillen contributed reporting.