Top Republicans were quick to dismiss the suggestion of putting off Election Day — but Democrats went further, calling it evidence that the president would stop at nothing to throw doubt on the validity of an election that he currently appears likely to lose.At this moment of coronavirus-driven insecurity, where do Americans stand on voting by mail? And how many might be persuaded, as the president argues, that the election’s very legitimacy is in doubt?Recent polling shows that Americans now overwhelmingly support universal access to mail-in voting. In national surveys from the past few months, all taken after Mr. Trump began attacking the idea as dangerous, upward of six in 10 respondents have said that they would favor making absentee voting universally available.But surveys also reflect how susceptible many people’s opinions can be to misinformation, when it comes to matters of fraud and vote security. For instance, 49 percent of Americans said in an ABC News/Washington Post poll in mid-July that mail-in voting was “vulnerable to significant levels of fraud.” That lines up cleanly with a Gallup poll from April that showed 49 percent of Americans thought expanding access to mail-in ballots would increase the prevalence of voter fraud.This despite the fact that studies have consistently proved voter fraud to be exceedingly rare — including in the five states that now conduct all their voting by mail.Lines tend to be longer in cities and other areas with particularly high rates of African-American and Latino voters — meaning that it is not always easy for people in these places to successfully cast ballots in person.If Mr. Trump were to successfully beat back access to absentee ballots, proponents of voting rights worry that it could disenfranchise these communities in particular.Republican state legislatures throughout the country have enacted a variety of voting restrictions since 2013, when the Supreme Court rolled back the Voting Rights Act. The Brennan Center for Justice, a pro-democracy watchdog group, has determined that in the past decade, 25 states have passed laws making it harder to cast a ballot.Amid the pandemic, those problems have often become especially acute — particularly in states like Wisconsin and Georgia, where voters in many precincts during this year’s primaries were forced to wait in line for hours after Republican officials in both states resisted expanding access to absentee voting.In many primaries, “the polling places were dramatically underequipped — there were far too few of them and there were fewer resources than needed,” said Wendy Weiser, who runs the democracy program at the Brennan Center. “We saw the problems compounded in more populous areas, and even more in urban areas that have higher concentrations of Black and brown voters.”But for now, it is primarily Republicans who have internalized Mr. Trump’s arguments about the dangers of mail voting — meaning that they, not Democrats, may be more likely to risk voting in person in November. The recent ABC/Post poll found that only 28 percent of Joseph R. Biden Jr.’s supporters saw mail voting as vulnerable to substantial fraud, whereas 78 percent of Mr. Trump’s supporters did.In a similar vein, while a slight majority of Mr. Biden’s backers said mail ballots would be their preferred method of voting this year, only 17 percent of Trump’s supporters said the same.Republican arguments about voter fraud are nothing new, and neither is the trend of Republican worries outpacing Democrats’ concerns. Four years ago, despite evidence to the contrary, seven in 10 Trump supporters thought that voter fraud was common, according to an ABC/Post poll taken on the eve of the 2016 election.This has led some observers to wonder whether, in areas where in-person voting during the pandemic becomes difficult or even impossible, Trump-driven skepticism about mail voting could disproportionately drive down Republican participation.“Maybe it’s an unintended consequence of what he’s saying,” said Amber McReynolds, who runs the National Vote at Home Institute and Coalition, a nonpartisan group devoted to expanding access to the ballot. “He’s assuming that his impact is on everybody, but it’s actually hurting his voters, probably. And the data shows that, because we’re seeing a decline in vote-by-mail requests among Republicans.”“He’s suppressing those that listen to him,” she added.Throughout the primaries, as Mr. Trump railed against the dangers of voting by mail, Democratic requests for mail-in ballots far exceeded Republican ones.Forty-one states already allow all voters to vote by mail, and seven of those send ballots to voters regardless of whether they request one, according to the Brennan Center.Ms. Weiser said that even if the general election in November were carried out relatively successfully, Mr. Trump’s habit of questioning the country’s electoral system could have far-reaching consequences.“His broad campaign to discredit the legitimacy of American elections, to say they’re rigged, to say that vote-by-mail is given to fraud — it will split America, and it will also be damaging to our elections and our standing in the world,” she said.Indeed, many Americans say they are more worried about false information being spread about elections than they are about illegitimate votes being cast. In January, months before Mr. Trump amped up his attacks on voting by mail, an NPR/PBS NewsHour/Marist College poll presented Americans with five factors that might pose a threat to “keeping voting safe and accurate.”Of those five options, Americans were most likely to say that misleading information was the biggest threat to the democratic process. Independent voters were particularly likely to be worried about being misinformed.