Voters, campaigns and election officials in four states holding contests Tuesday are braced for a presidential primary day unlike any in memory, as the surging threat of the novel coronavirus has forced major changes at voting locations, rattled poll workers and left voters worried about how to cast their ballots.

In Arizona, Florida, Illinois and Ohio, election officials have raced to replace poll workers who have said they will not show Tuesday, supply thousands of precincts with sanitizing supplies, and notify voters whose polling locations, many in senior facilities, have been moved as a result of the pandemic.

Voters, meanwhile, have flooded information hotlines. Among their urgent questions: where to vote, how to deliver a ballot if they are under quarantine and how to vote if they registered while attending a college that is now closed.

As the coronavirus spreads, the Democratic Party of Puerto Rico announced Sunday that it would seek to postpone the territory’s March 29 primaries, joining Louisiana and Georgia. One New York election official said Sunday that discussions are underway about whether to delay that state’s contests.

The rapidly changing landscape left officials worried about the threat of two equally dire outcomes Tuesday: chaos at voting places, with diminished staffs causing long lines and increasing the risk of exposure to the deadly virus; or low turnout levels fueled by public fear.

Either scenario could roil the Democratic presidential contest and complicate former vice president Joe Biden’s efforts to secure the nomination over Sen. Bernie Sanders (I-Vt.). Among the four states voting Tuesday, 577 delegates are up for grabs.

“I really don’t have any idea how it will go,” said Wendy Sartory Link, supervisor of elections in Palm Beach County, the second-largest of Florida’s 67 counties.

Of roughly 3,500 poll workers originally signed up to work at 435 voting locations in Palm Beach, about 650 have canceled amid fears about the virus, Link said.

That means some polling locations slated to have 10 workers on hand could instead have seven, or even five. It also will mean fewer check-in stations and, if turnout is robust, longer lines, she said.

Link said her office successfully notified all voters whose precincts were moved as a result of the pandemic, for instance if the original location was in an assisted-living facility. Gov. Ron DeSantis (R) on Friday ordered locations near certain vulnerable populations moved.

One of the biggest challenges, voting advocates said, is just making sure people know how to cast their ballots.

Marcia Johnson-Blanco, co-director of the Voting Rights Project at the Lawyers’ Committee for Civil Rights Under Law, said her team is making its way through a mountain of calls from concerned voters, including college students who registered on campus but are home now and self-quarantined individuals not sure how to deliver their ballots in states that don't allow third parties to handle them.

“We’re just in uncharted territories on so many fronts,” Johnson-Blanco said.

On Sunday, people voting early in Ohio, Florida and Illinois crowded into polling locations at higher-than-usual rates — in many cases to avoid potentially longer lines Tuesday.

Lisa Hamilton, 55, a teacher’s aide from Shaker Heights, Ohio, said she voted Sunday because she is in remission after battling multiple myeloma and was worried about her vulnerability to the coronavirus. But she and other voters encountered crowds at the Cuyahoga County Board of Elections headquarters, with wait times between 30 and 45 minutes, according to election officials.

“I have my Purell, I have my tissue that I picked up the pen with and voted with, I asked the person behind me, who was coming too close, ‘Please give me some more space,’ ” Hamilton said. “I don’t know if I offended anybody, but I am worried about being out here with so many people. But at the same time I think it’s so important.”

At an early-voting site in West Palm Beach, Fla., Jane Murphy, a middle school assistant principal, sanitized her hands twice in between casting her vote for Biden, directed by poll workers to a large container of hand wipes by the door.

“We have to be responsible citizens, even in a pandemic,” Murphy said. “We have responsibility for the direction our country is taking, and this is a way to live up to that responsibility. It’s a way for our voices to be heard.”

Marc Elias, a Democratic election lawyer in Washington, said Tuesday represents the country’s first test of how to administer an election in the middle of a pandemic — and is likely to provide a road map for the necessary preparations for the more critical general election in November.

A bad day, he added, “will feed not only a narrative that people are waiting a long time but also that there's a public health crisis as well.”

Catherine Turcer, executive director of Common Cause Ohio, said the public’s fears could overtake their desire to vote — though she encouraged people who feel comfortable to turn out.

“We’re asking people to go into pretty confined conditions, and even with all sorts of wipes and the things that can be done to make things safe, it is anxiety-provoking,” she said.

In France, voter turnout in the first round of local elections Sunday was down 20 points compared with 2014, according to French media, as some questioned President Emmanuel Macron’s decision to proceed with the vote.

So even as state and local officials in the United States intensified their warnings about the coronavirus threat Sunday, they also sought to reassure voters that casting their ballots was safe.

Ohio Gov. Mike DeWine (R) ordered all bars and restaurants to close at 9 p.m. Sunday until further notice, calling it a “life and death” decision. But like leaders in the other three states holding elections this week, he said there were no plans to delay the primaries.

“It is important for us to be able to exercise our constitutional rights,” DeWine said, “and to interrupt an election in the middle of it poses some very, very serious consequences.”

In a video posted Friday on YouTube, Ohio Department of Health Director Amy Acton said it was “absolutely” safe for people who are healthy to serve as poll workers.

“We need you,” Ohio Secretary of State Frank LaRose said in the same video. “This is your patriotic duty. . . . A no-call, no-show on Tuesday is absolutely not acceptable.”

Still, Ohio and Illinois are still struggling to recruit enough poll workers to prevent disruptions Tuesday, advocates and officials said. In Cook County, Ill., Clerk Karen A. Yarbrough tweeted that all training requirements will be waived for volunteers.

At the county level, officials are taking a variety of precautions, but some said they have struggled to provide supplies for all voting locations.

In some Ohio jurisdictions, cotton swabs will be available to use on screen-based voting machines. In Franklin County, the most populous in the state, voters will have access to finger cots, also known as finger gloves or finger condoms, as they cast their ballots.

Paul Lux, supervisor of elections in Okaloosa County, in Florida’s Panhandle, said he wasn’t able to secure hand sanitizer for all 42 voting locations. Lux also learned Sunday that local officials had just closed two city recreation centers slated to serve as voting locations. Scrambling to find alternatives, he was able to persuade city leaders to cordon off portions of both buildings to allow voting to proceed.

“Tuesday cannot get here fast enough!” Lux wrote in an email.

Meanwhile, key states due to vote in April were weighing their own emergency decisions.

Douglas A. Kellner, New York State Board of Elections co-chairman, said talks were underway with the governor’s office and legislative leaders about postponing the presidential primary from April 28 to June 23.

In Wisconsin, which is scheduled to hold its primaries April 7, the elections commission asked local clerks to mail absentee ballots to voters in nursing homes. Officials urged all voters to cast absentee ballots if possible.

Back in Florida, Michele Levy, a poll worker near Orlando, said she will show up Tuesday as a matter of principle. “The voters need us now,” said Levy, a board member with the League of Women Voters of Florida.

She said the county has not provided sanitizing supplies for the voting location where she’ll work Tuesday, Orange Technical College in Winter Park, so she is encouraging voters to bring their own.

“I intend to wash my hands a lot and just, you know, hopefully things will go well,” she said. “I don’t know what else to do. We’re all a little concerned, but we’ll be there.”

Joanna Connors in Cleveland, Lori Rozsa in Palm Beach, Fla., and Isaac Stanley-Becker in Washington contributed to this report.