The political conventions over, Joe Biden now leads Donald Trump in the race for the White House by 50%-43%, the new USA TODAY/Suffolk University Poll finds. That seven-point advantage has narrowed from the 12-point edge he held in June. As Labor Day looms, launching the campaign's final sprint, the survey finds significant skepticism about whether the election itself can be trusted. If their candidate loses, one in four voters say they aren't prepared to accept the outcome as fair and accurate – a signal of potential trouble ahead for a nation already engulfed in a deadly pandemic and riven over issues of racial justice. "I'm definitely worried about it," said Curtis Saffi, 38, an independent from Hampton, Georgia, who plans to vote for Biden. "Whether it's the post office or someone meddling in our elections, you really don't know." In all, 28% of the former vice president's supporters say they aren't prepared to accept a Trump victory as fairly won; 19% of President Trump's supporters say they aren't prepared to accept a Biden victory as legitimate. What's more, an overwhelming 83% of Republicans say they are at least somewhat concerned that mail-in voting will lead to voter fraud; 62% are very concerned. That's an assertion Trump has been hammering without offering evidence, and one that's disputed by election experts and academic studies. "It will be 100% botched for sure," predicted David Brockman, 38, a Trump supporter from Columbus, Indiana, who was among those polled. "I have no doubt." Only a third of Democrats are concerned about mail-in voting being open to fraud. 'War games':Experts role-played the Trump vs. Biden election. Their finding? Brace for a mess The poll of 1,000 registered voters, taken Friday through Monday by landline and cell phone, has a margin of error of plus or minus 3.1 points. Suspicion over the count may be fueled by a divide over just how Americans plan to cast their ballots. Republicans are more than twice as likely as Democrats to say they'll vote in person and on Election Day, 56% compared with 26%. Democrats are more than twice as likely as Republicans to plan to vote absentee or by mail, 47% compared with 21%. For many, a referendum on the incumbent Trump defines the contest. Among the president's supporters, 83% say they are voting for him; just 11% are voting against his opponent. "I love him to death because he's not a politician," said Greg Hogue, 60, from Aldo, Texas."He sticks foot in mouth, but you know what? He can get through all the bullcrap." Watching the Republican convention last week "solidified" his support of Trump, Hogue said. Among Biden backers, 59% say they are voting for him but one in three, 33%, say they are voting against his opponent. In follow-up phone interviews, some described the dangers of a second Trump term in grave terms. "I think there's just something about Trump's rhetoric that is incredibly anti-democratic and worrying, beyond just the policies," said Antonio Gonzalez, 31, a Democrat from Portland, Oregon. "I genuinely worry about what would happen with four more years of him in office." The research and design consultant was "heartened" by Biden's performance at the Democratic convention, he said. "He did a good job really articulating himself as a candidate and what he stood for," which Gonzalez called particularly important given Trump's depiction beforehand of Biden as "incoherent." The competing conventions, both revamped on the fly because of COVID-19, had almost precisely the same impact in energizing partisans. Two-thirds of Democrats and two-thirds of Republicans said the conventions made them more likely to support their party's nominees. But the Democratic convention fared somewhat better in persuading independents. By a narrow two points, 33%-31%, independents said watching the conventions made them more likely rather than less likely to support Biden. But by nine points, 38%-29%, they said they made them less likely rather than more likely to support Trump. By some measures, Biden's situation is similar to that of Democratic presidential nominee Hillary Clinton four years ago. In a USA TODAY/Suffolk Poll taken in August 2016, Clinton led Trump by seven points. (That ballot test included third-party candidates; Biden now leads Trump by five points in a ballot that includes third-party options.) In that election, Clinton won the popular vote but lost the Electoral College to Trump. "I'd say Biden is no better off at this point," said David Paleologos, director of the Suffolk Political Research Center, though he added that there are significant differences between the two contests. "Hillary was more polarizing and less likable than Biden in terms of the favorable/unfavorable ratings. However, Clinton had more enthusiasm than Biden does today, which makes the analysis a bit dicey." A divide over protests and violence The nation is more fraught than it was four years ago. The death toll among Americans from the coronavirus is climbing toward 200,000, and thousands of protesters have taken to the street to protest police treatment of Blacks. Some cities have seen looting and arson. About half of those surveyed, 49%, said police shootings of Blacks reflected individual actions and misdeeds, while 41% said they reflected systemic racism in American society. But there was a sharp partisan split: 83% of Republicans saw individual misdeeds; 73% of Democrats saw systemic racism. A solid majority of Americans, 57%, said peaceful demonstrations should continue, even though violence has followed in some cities. Thirty-six percent said peaceful demonstrations should stop for now, because violence has followed in some cities. Kenosha:Trump claims credit for bringing calm to Kenosha in visit criticized as politicizing racial unrest Protests:Biden, Trump campaigns spar over blame for violent protests On this, too, partisanship opened a deep divide. More than three-fourths of Democrats said the peaceful demonstrations should continue. Nearly six in 10 Republicans said they should stop. "We need to get this situated – the violence, the looting, the rioting," said Brockman, the Trump voter from Indiana. "I mean, we're going to be in a civil war within the next six months if something doesn't happen." But Dana Carbonell, 35, a Democrat from Weehawken, N.J., supported the demonstrations, though not the violence. "I mean, the only way that change has happened in this country is by people taking it to the streets and making their voice be heard," she said. In their interviews, Carbonell and Brockman were in accord on one thing. "Honestly, it's really important," he said of the November election. She agreed. "One way or another, it's going to define our time," she said.