Voters fill out ballots at Riverside University High School during the presidential primary election, held amid the coronavirus disease (COVID-19) outbreak, in Milwaukee, Wisconsin, US, April 7, 2020. [Photo/Agencies]

MILWAUKEE - Wisconsin held its presidential primary as planned Tuesday, contradicting a state-wide stay-at-home order and defying concern that the election could expose thousands of masked voters and poll workers to the coronavirus.

Long lines, shuttered polling stations and workers in hazmat suits marked the most unsettling and confounding contest of the 2020 Democratic presidential nomination race: a vote at the height of a deadly pandemic.

Democratic officials had sought to postpone the election, featuring frontrunner former vice president Joe Biden and leftist Senator Bernie Sanders, but were overruled by the top state court.

The US Supreme Court also intervened, barring an extension of voting by mail that would have allowed more people to cast ballots without going to polling stations in person.

Both courts have conservative majorities.

With the Midwestern state ignoring calls to postpone the primary, as 15 other states have already done, many Wisconsinites were being forced into an agonizing decision: risk their health to fulfill their democratic right, or stay safe by staying at home.

In Milwaukee, voter options were drastically reduced due to a shortage of election staff.

The city of 600,000 normally has some 180 polling locations open, but that number reportedly has been reduced to just five, prompting long lines in an era of social distancing.

Wisconsin's chief election official Meagan Wolfe called on voters to be "careful and patient" at the polls.

"If you are ill and still need to vote on Election Day, curbside voting options are available," she said in a statement.

At a Milwaukee polling station, staff set up lanes where some people could vote from their cars.

With the new precautions in place and most polling locations closed, wait times in Milwaukee soared. The line at the Riverside University High School was hundreds of yards (meters) long, and well beyond one hour.

A woman in line in Milwaukee held up a cardboard sign bearing a message reading: "THIS IS RIDICULOUS."

The vote has prompted scenes unimaginable just three months ago, including elections chief Mary Magdalen Moser clad in hazmat gear as she operated her polling station in Kenosha.

More than 2,500 people have tested positive for coronavirus in Wisconsin and 92 have died. The nationwide death toll has topped 12,700.