Four-day event set to include formal nomination of Joe Biden as the Democratic challenger of US President Donald Trump.

A presidential primary season like no other will culminate this week for the Democratic Party in the United States in an unprecedented, mostly digital convention that is set to cement Joe Biden as the official candidate tasked with taking on President Donald Trump in a November election. 

Only essential staff will be on the ground at the convention centre in Milwaukee, Wisconsin, a pivotal swing state that had spent millions of dollars preparing to host the high-profile event, which runs from August 17 to 20, before it was scaled back in light of the pandemic.

The former vice president and his allies have every reason to feel bullish. Polls show Biden has built an expansive lead in nearly every battleground state that Trump won narrowly in 2016, as the Republican’s approval numbers tumble amid the coronavirus pandemic. For the first time in a decade, retaking the Senate - and full control of Congress - is within sight.

Yet interviews with more than a dozen Democratic officials, activists and voters reveal deep anxieties that Trump will make voting as difficult as possible during the pandemic, and should he lose the vote, he won’t accept its outcome.

Biden himself has called it his biggest fear. Former President Barack Obama sounded the alarm on Friday, saying on Twitter the Trump administration is “more concerned with suppressing the vote than suppressing a virus.” And eight of 10 Democrats are concerned about voter suppression, according to a Reuters/Ipsos poll in late July.

Trump has railed against voting by mail for months, proclaiming without evidence that it will lead to fraud, and on Thursday all but acknowledged he was blocking Democratic demands for additional funding for the post office because of his opposition to mail-in voting.

“We can’t predict what’s going to happen other than the closer we get to the election, the more desperate Trump and his campaign will become,” said Rodell Mollineau, an adviser to Unite the Country, a political action committee that backs Biden.

Tim Murtaugh, a spokesman for the Trump campaign, said the president wants a “free and fair” election, adding that it is Democrats who are inviting “chaos and the very real possibility of fraud” by trying to expand voting by mail.

Democrats and voting rights groups say mail-in voting can help protect voters from the coronavirus, and that a failure to guarantee that option during the pandemic will disenfranchise millions of Americans, especially the poor and African-Americans who tend to vote Democratic.

Some say Biden’s commanding edge in the polls only makes them more nervous. They worry that increasing cases of COVID-19 could keep voters away from polling places, particularly if Biden is perceived as coasting to an easy win.

“If Biden is up by 10 points, how likely are you to risk your life to pull that lever,” Stefan Smith, who was a top digital strategist for Pete Buttigieg’s presidential campaign.

At about this time in 2016, then Democratic presidential nominee Hillary Clinton had around a five-point lead in various polls and still lost the election three months later, partly due to the first decline in African-American turnout in 20 years.

Michigan Democrat Patty Leitzel, who lives in politically divided Macomb County, said she is still traumatized by the win Trump squeaked out in her state four years ago and worries he could do so again - as do the voters she talks to on a regular basis.