President Donald Trump may have an apparent lead over former Vice President Joe Biden at the end of Election Day, and still solidly lose by week’s end, a new report shows.

Media outlets and political figures should alert the public to this possibility in advance so people have a clear understanding of these implications on election night and the days that follow as swing-state mail-in votes are counted, researchers say.

“The size of these shifts will depend on several factors: differences in rates of voting by mail between Trump and Biden supporters, when people mail in their ballots, and each state’s rules for receiving and counting votes made by mail,” says Katherine Ognyanova, an assistant professor of communication at Rutgers University-New Brunswick’s School of Communication and Information and coauthor of the new paper.

“Given the current election procedures and delays in counting mail ballots, the ‘blue shift’ seems especially likely in the key battleground states of Michigan, Pennsylvania, and Wisconsin,” Ognyanova says.

Texas, North Carolina, Alaska, Pennsylvania, New Hampshire, Ohio, Wisconsin, Michigan, and Nevada are the most likely states to have substantial vote shifts toward Biden, potentially shifting both the Electoral College and popular votes, the researchers say. All nine states allow mail-in ballots to arrive after Election Day or do not start counting until Election Day.

With an unprecedented number of mail-in votes, many states will face the logistical challenge of counting ballots.

The survey shows there are considerable differences in candidate preference among Americans planning to vote in person and vote by mail. In-person voters are more likely to support Trump, while those who plan to cast mail-in ballots lean toward Biden.

Trump leads by 68% to 23% among those who say they are “very unlikely” to vote by mail and by 50% to 39% among all but those who say they are “very likely” to vote by mail. Biden, however, leads among all likely voters by 50% to 40%.

“We strongly recommend that media outlets and political figures set public expectations accordingly in advance,” says Ognyanova. “If Americans take election night results as final, the later swing as mail votes are counted could undermine public belief in the legitimacy of the election.”

The COVID-19 Consortium for Understanding the Public’s Policy Preferences Across States, which published the paper, is a joint project of Rutgers University, Northeastern University, Harvard University, and Northwestern University. The consortium has released sixteen reports and has charted public opinion related to COVID-19 topics since late April.