A potentially crucial Democratic primary election has been overshadowed by accusations of voter suppression and even murder, as residents of Wisconsin were forced to decide between forgoing their chance to vote or risk being exposed to coronavirus.

After the state’s conservative top court refused a call from Democrats to suspend the vote or else make available postal voting for everybody, thousands lined up outside overcrowded polling stations.

They were voting not only for their pick between Joe Biden or Bernie Sanders to take on Donald Trump, but a raft of local contests.

Democrats had said the decision by the court, which was supported by Republicans, would have the impact of lowering voter turnout, a point made by senator Cory Booker, who tweeted: “Milwaukee is home to the largest African-American community in Wisconsin. Don’t tell me that forcing people to choose between their health and their right to vote today is anything but an appalling act of voter suppression.”

His words were retweeted by Susan Rice, who served as Barack Obama’s national security adviser, and who added her own words to those of Mr Booker – “Actually, murder”.

Wisconsin primary Show all 13 1 /13 Wisconsin primary Wisconsin primary Steve Merriweather waits to vote inside Riverside University High School during the Wisconsin primary REUTERS Wisconsin primary Aaron Lipski, the assistant chief of the Milwaukee Fire Department, stands in a tyvec suit as he monitors health an safety at a polling station inside Hamilton High School during the Wisconsin primary REUTERS Wisconsin primary Voters practise social distancing in Milwaukee during the Wisconsin primary REUTERS Wisconsin primary Voters wait to cast their ballots at a polling station in Milwaukee during the Wisconsin primary REUTERS Wisconsin primary Rachel Messenger wears a sign reading 'Thank you for risking your life to vote' outside Riverside University High School in Milwaukee during the Wisconsin primary REUTERS Wisconsin primary Voters in masks wait to cast their ballots in Milwaukee during the Wisconsin primary REUTERS Wisconsin primary A line of voters outside Riverside University High School in Milwaukee during the Wisconsin primary REUTERS Wisconsin primary Voters filling out their ballots in Milwaukee during the Wisconsin primary REUTERS Wisconsin primary People wearing protective masks wait to vote in Milwaukee during the Wisconsin primary REUTERS Wisconsin primary A City of Milwaukee Election Commission worker takes a break during the Wisconsin primary AP Wisconsin primary City of Milwaukee Election Commission workers process absentee ballots during the Wisconsin primary AP Wisconsin primary Voters waiting to cast their ballots in Milwaukee during the Wisconsin primary EPA Wisconsin primary A line of people wait in their cars for their turn to vote at Riverside High School in Milwaukee during the Wisconsin primary EPA

The process appeared all the more strange given a separate federal court ruling that deemed results not be made public until April 13. That was part of a move by district judge William Conley, who granted a request from the Wisconsin Elections Commission to extend absentee voting amid concerns about both voters and election officials being exposed to the virus.

Wisconsin, and in particular Milwaukee, has emerged as a new hotspot for the virus, with at least 92 deaths and more than 2,500 infections. Reports have shown a disproportionate number of those people are African Americans.

Mr Sanders, 78, was among those calling for the election to be postponed.

“It’s outrageous that the Republican legislative leaders and the conservative majority on the Supreme Court in Wisconsin are willing to risk the health and safety of many thousands of Wisconsin voters tomorrow for their own political gain,” he said. “Let’s be clear: holding this election amid the coronavirus outbreak is dangerous”

His rival, Mr Biden, 77, did not make any such demand. “There’s a lot of things that can be done; that’s for the Wisconsin courts and folks to decide,” he said.

As it is, the contest may be Mr Sanders’s last hand in his bid to become the Democratic nominee. Going into the election, his delegate count stood at 914, compared to 1,217 for Mr Biden.

Coronavirus in numbers

Wisconsin has 90 delegates, but it unclear how many Mr Sanders will bag. A poll published this week by Marquette University Law School, gave the former vice president a lead of as many as 28 points over the Vermont senator.

The state, where Mr Sanders defeated Hillary Clinton in 2016, is among the most crucial battlegrounds as the two parties prepare for November.

Mr Trump squeezed by Ms Clinton to secure the state and its 10 electoral points by just 22,000 votes four years ago. It was one of three states, the others being Wisconsin and Pennsylvania, he won against the odds to take the White House.

On Tuesday, the significance of the contest was not lost on those taking part.

Pregnant and infected with the coronavirus, 34-year-old Hannah Gleeson was still waiting for the absentee ballot that she requested last week.

“It seems really unfair and undemocratic and unconstitutional, obviously,” said Ms Gleeson, who works at an assisted-living centre in Milwaukee. “It seems really absurd. And I think it’s voter suppression at its finest.”

The race pitted the Democratic and Republican parties against each other over central questions about how elections should be managed in a crisis. Democrats complained that the state was risking the health of its citizens by not postponing the election. Republicans insisted that the election should go on as scheduled — including voting for a pivotal state Supreme Court seat.

After several hours of voting, there were signs that the Wisconsin test was not going well.

In Milwaukee, the state’s largest city operated just five of its 180 traditional polling places, having been forced to scale back after hundreds of poll workers stepped down because of health risks. The resulting logjam forced voters to wait together in lines spanning several blocks in some cases. Many did not have facial coverings.

Meanwhile, Wisconsin Assembly speaker Robin Vos, a Republican, wore a mask, gloves and other protective gear as he sought to assure voters it was “incredibly safe” to vote in person.