As returns came in on election night in Florida in 2018, the Republicans running for governor and the Senate took narrow leads in races that were too close to call.
Over the next days, their Democratic opponents began closing the gaps as mailed-in votes were counted. President Trump raised an alarm. Demanding that the races be called for the Republicans, Rick Scott and Ron DeSantis, he tweeted falsely that “large numbers of new ballots showed up out of nowhere,” adding: “An honest vote count is no longer possible-ballots massively infected. Must go with Election Night!”
Nothing was fraudulent about the ballots tallied in the days after Election Day. And neither Democrat went on to win his race. Yet Mr. Trump has never let go of a baseless accusation that Democrats use mail voting to “steal” elections, a piece of disinformation he has promoted all year, including at the Republican National Convention.
Now, with the coronavirus pandemic driving an explosion in absentee voting, and polls suggesting that far more Democrats than Republicans plan to vote by mail, a nightmare scenario haunts Democratic strategists and elected officials.
What if early results in swing states on election night show the president in the lead because most Republicans voted in person, yet in the days afterward, as mail ballots that tilt heavily Democratic are tallied, states flip to Joseph R. Biden Jr.?
Would Mr. Trump claim premature victory — as he did on behalf of the two Florida Republicans and dangled as a possibility in a tweet in July: “Must know Election results on the night of the Election, not days, months, or even years later!”
Would the president, joined by allies in the G.O.P. and the news media, sow distrust in the election by arguing that mail ballots that shift states away from him are “rigged”?
Mr. Trump has been pushing denunciations of mailed-in votes for months, and his penchant for conspiracy theories is only intensifying, such as saying this week that people in “dark shadows” are behind Mr. Biden’s campaign. The nightmare scenario in November is worth preparing for, many Democrats say.
“We’ve certainly seen candidates trying to get out in front of a narrative and declare victory when all the votes have not been counted,” said Jocelyn Benson, Michigan’s secretary of state, a Democrat whom Mr. Trump has attacked for promoting mail voting.
Ms. Benson and other Democrats in Michigan and Pennsylvania, both key battlegrounds, are trying to change election laws that prohibit absentee ballots from being processed or counted before Election Day. As of now, mail-in votes from large Democratic cities like Philadelphia, Milwaukee and Detroit are not reported until after in-person votes, sometimes days later. Party lawyers are girding for a worst-case scenario in which Mr. Trump fights in courts and state legislatures after declaring a premature victory.
“There has been (rightly) a lot of concern about this,” J.J. Balaban, a Democratic consultant in Pennsylvania, said in an email.
In Michigan, Ms. Benson predicted that three million votes would be cast by mail this year, 60 percent of the total. She has called for changes to let election clerks process absentee ballots early — opening envelopes, contacting voters if ballot signatures don’t match registrations, and beginning the counting. If the changes don’t pass in the Republican-led Legislature, full results may not be known until the Friday or Saturday after Nov. 3, Ms. Benson said. “Time is running out.”
Currently, 12 states do not allow mail-in ballots to be processed before Election Day, including the battlegrounds of Michigan, New Hampshire, Pennsylvania and Wisconsin.
A Democratic data group backed by Michael R. Bloomberg said this week that it was likely that Mr. Trump would appear to have won on election night by a landslide, a scenario it called “a red mirage.”
“We are sounding an alarm and saying that this is a very real possibility, that the data is going to show on election night an incredible victory for Donald Trump,” Josh Mendelsohn, the chief executive of the group, Hawkfish, told “Axios on HBO.” The company’s survey of registered voters concluded that twice as many planned to cast a ballot by mail as ever before, and that they were mostly Biden supporters.
A spokeswoman for the Trump campaign, Thea McDonald, called Democrats’ concerns about the president prematurely declaring victory “an unsubstantiated conspiracy theory,” adding, “President Trump and his campaign are fighting for a free, fair, transparent election in which every valid ballot counts — once.”
As Mr. Trump demonizes mail ballots, many of his supporters do not plan to use them.
An NBC/Wall Street Journal national poll last month found that nearly half — 47 percent — of supporters of Mr. Biden planned to mail in their votes, compared with two-thirds of Trump supporters — 66 percent — who planned to vote in person on Election Day.
In some states, the discrepancy is even more stark. A recent Marquette Law School poll of Wisconsin, another swing state, found that among voters planning to cast a mail ballot, Mr. Biden was favored by 67 percentage points. Among those who planned to vote on Election Day, Mr. Trump led by 41 points.
Mr. Trump himself casts his own Florida ballots as an absentee voter. He has claimed a distinction between “good” absentee ballots and “bad” mail-in ballots, but there is no meaningful difference. His real target seems to be certain states — which this year include California, New Jersey and Utah — where all active registered voters are sent mail-in ballots, not just ballot request forms. Thirty-four states allow all voters to use an absentee ballot without an excuse, mailing it back or dropping it off.
Elections experts say that absentee or mail voting is potentially more subject to instances of fraud than in-person voting, but that states with a history of all-mail voting have a minuscule number of cases. Wide-scale cheating that could swing a close race would be easy to detect.
“Imagine if you tried to change the outcome in Pennsylvania; you’d need a widespread conspiracy,” said Richard L. Hasen, an election law expert at the University of California, Irvine.
Even before Mr. Trump injected new partisanship into mail voting, election analysts identified a “blue shift” in how late-counted absentee ballots tend to boost Democratic candidates.
On election night of the 2018 midterms, a predicted wave of Democratic gains looked like a wipeout. But as mail ballots were tallied in the days and weeks afterward, Democrats kept winning close races. Their net gains in the House went from an apparent 26 seats on election night to 41.
“We’re likely to see a significantly dramatic blue shift in multiple states because of the virus and the political response to the virus,” said Edward Foley, an election law expert at Ohio State University, who coined the term “blue shift.”
“How will the public process the concept that election night may end in uncertainty, and this phenomenon is not fraud, it’s just the counting process?” he said.
While TV viewers are used to election night projections of who has won, some broadcast and digital journalists are discussing ways to clearly inform voters that results may be incomplete.
A claim of victory on election night by Mr. Trump, before results are certified by officials, would have no legal effect, Dr. Hasen said. “That said,” he added, “it could have a great political effect and convince his most ardent supporters that he has won the election and any changes in the counts are due to fraud. That’s really a huge concern.”
Anthony Spano, a Trump supporter in Old Forge, Pa., said the president was “so right” when he warned of potential fraud by Democrats. “If they think there’s unrest now, just wait to see if they try to steal this election,” said Mr. Spano, who has worked as a truck mechanic. “Personally, I think people that are nonviolent, we’re going to get very violent.”
Partisan lawsuits are already flying in multiple states around voting procedures, and legal and political challenges are sure to come where results are razor-thin.
Mail ballots, whose use soared in primaries this year because of the pandemic, have been subject to high rejection rates because of human errors: omitted signatures, missed deadlines and missing postmarks. For many Democrats, recent fears that the Postal Service could fail to deliver ballots on time to be counted could potentially swing the pendulum back toward in-person voting.
The party is shifting from its springtime message, that mail voting is safer, to one urging voters to request and return absentee ballots early, and if possible to vote in person. Michelle Obama told viewers of the Democratic National Convention, “We’ve got to vote early — in person if possible.”
In Pennsylvania, Secretary of State Kathy Boockvar, a Democrat, and other officials have called for a new law to allow absentee ballots to be opened and processed as early as three weeks before Election Day. Those results would be reported at the same time as Election Day in-person votes.
The point is “to try to avoid candidates making false claims about wins and losses,” said Representative Madeleine Dean, a Democrat from the Philadelphia suburbs who backs the legislation.
Republican state lawmakers partly support the reform, calling in a bill for early processing of mail ballots the Saturday before Election Day. For now, the bill is deadlocked because Democrats oppose other voting changes sought by Republicans, such as eliminating ballot drop-off boxes.
“I worry about a deadlock and not doing the right thing for our elections,” Ms. Dean said. “I’m hoping cooler heads will prevail.”