Voters in Chicago on Tuesday confronted shuttered precincts, missing poll workers and confused officials struggling to administer an election during a public health crisis, a chaotic situation that voting advocates said created barriers for those trying to participate in the state’s Democratic presidential primary.

The problems in Illinois appeared to be the most acute examples of issues in three states that voters faced related to the coronavirus outbreak. Arizona, Florida and Illinois chose to proceed with their contests this week, while a fourth state — Ohio — postponed in a controversial, 11th-hour move on Monday night.

The last-minute challenge facing election officials was unprecedented, experts said: making sure people could visit polling locations and cast their ballots safely — even as health officials were issuing dire warnings about the need to stay isolated to stop the spread of covid-19, the disease caused by the virus, advocates say.

In locations around Chicago, voters arrived at polling places to find no election judges to run their precincts, or no hand sanitizer or wipes for voting machines. Some voting locations in Palm Beach County, Fla., where officials said there appeared to be lower than usual voter turnout on Tuesday, had not opened by late morning. And in Arizona, some people were directed to vote at municipal buildings that were otherwise closed to the public, causing confusion.

Even in Ohio, some voters showed up at polling sites on Tuesday morning only to learn that in-person voting was delayed until June 2. In some locations, advocates said, no signs were posted to indicate the change, and a hotline for voters to report problems was flooded with calls.

The challenges Tuesday intensified questions about how subsequent primaries — and the general election — can go on if the pandemic does not subside. Many have called for states to conduct all voting by mail, but there are questions of whether Congress has the votes to pass such a mandate, as well as about states’ abilities to implement such a massive new initiative in a matter of months. Only three states — Colorado, Washington and Oregon — currently run elections with mail-in ballots only.

“We’ve been hearing from countless voters who are unsure about the status of voting today,” Kristen Clarke, president and executive director of the National Lawyers’ Committee for Civil Rights Under Law, said on a conference call with reporters.

“It’s unlike anything we have ever seen before,” Clarke said of the situation in Ohio, where voters “went to bed” on Monday night unsure whether the elections would take place.

Clarke said the problems Tuesday offer a clear warning to state and local officials to better prepare for the coming primary contests and the November general election. She urged them to expand access to voting by mail, including offering postage-paid envelopes, lifting restrictions on who may return ballots for homebound voters, and putting an end to signature-matching procedures that she said amount to “junk science” and lead to legitimate ballots being tossed.

“Eighteen states impose restrictions and barriers on voters who seek to cast absentee ballots. Now’s a moment for those states to abandon those restrictions,” Clarke said.

Democratic National Committee Chairman Tom Perez also urged states to adopt vote-by-mail, no-excuse absentee voting and extended polling place hours.

“As our country deals with the uncertainty of COVID-19, it is critical that states provide clarity and not confusion, which could lead to disenfranchising voters,” Perez said in a statement.

Democrats in the states that went forward with primaries on Tuesday reported a sharp rise in the use of early voting and vote-by-mail options. In Arizona, there were more early votes by Democrats this year than total votes cast in the party’s 2016 primary. And in Florida, 141,560 more Democrats voted by mail this year than they did four years ago.

Complaints from voters who went to polls in person raised questions about states’ decision to proceed with Tuesday’s primaries amid a deepening health crisis. Yet criticism also poured in over Ohio’s decision to postpone its primary, a sign of election officials’ difficult position.

“Our democracy needs to continue,” said Lori Lightfoot, the mayor of Chicago. “But as we have been winnowing the size of gatherings, people are necessarily nervous, and that has affected the availability of polling places, as well as the availability of election judges.”

Lightfoot issued a warning to states with primaries coming up, urging them to begin planning now, and to expand options for voters to participate early and by mail. The city, she said, received an “unprecedented number of applications to vote by mail.”

Five states have now delayed their contests — Georgia, Kentucky, Louisiana, Maryland and Ohio — with others expected to follow suit in the coming days.

Ohio’s handling of its primary served as a cautionary tale.

State officials announced Monday afternoon that they would seek to postpone the election because of the coronavirus. As county officials spread the word that no in-person voting would take place on Tuesday, a judge in Franklin County rejected a delay.

In the end, with the backing of Gov. Mike DeWine (R), the Ohio Department of Health ordered polls closed, citing a “health emergency.” Election officials said in-person voting would take place on June 2.

The Ohio Democratic Party on Tuesday asked the state Supreme Court to intervene to ensure that eligible voters would have “an adequate alternative means of voting given the suspension of voting at the polls.” The motion reflects widespread skepticism that Ohio’s secretary of state has authority to set up a new date for in-person voting without action by the legislature or a court.

Voters and candidates were dismayed by how events unfolded.

Jeffrey A. Sites, a Democrat running in the primary to challenge Rep. Jim Jordan (R-Ohio), said that while it was “crucially important” to protect people’s health, the whiplash from officials “served Ohioans and the democratic process poorly.”

“I believe we’re owed an accounting of how exactly the fiasco of the last 24 hours came about,” Sites wrote in a statement posted on Facebook.

The confusion created uncertainty for the campaigns of former vice president Joe Biden and Sen. Bernie Sanders (I-Vt.), who were vying for the 441 delegates that were up for grabs in the remaining three states Tuesday.

Biden had hoped to capitalize on the momentum he built in the past two weeks, with help from older voters who typically vote in large numbers but are vulnerable to the coronavirus. In Florida, some voters received a robo-text from his campaign on Tuesday asking: “Can you vote safely for Joe?”

Biden’s advisers sought to preempt any notion that lower turnout would undermine Tuesday’s results.

“While voter turnout on Election Day itself may be lower due to COVID-19 concerns, we believe that, with early vote and vote by mail, overall turnout will be roughly on pace for 2016 in Arizona and Florida and roughly on pace for 2018 in Illinois, and that voter turnout in all three states will reflect the population at large,” Biden deputy campaign manager Kate Bedingfield wrote in a memo.

Tuesday’s voting problems appeared to be the most widespread in and around Chicago.

At a precinct in Barrington, a northwest suburb, election judges did not show up when doors opened at 6 a.m., frustrating would-be voters. A spokesman for local election officials said replacements were sent “shortly before 9 a.m.”

By the end of the day, the Cook County Clerk’s Office extended voting in 40 suburban precincts by one hour to 8 p.m. because of the extensive issues. Suburban Cook County saw its lowest voter turnout in 12 years: About 202,000 voters came out Tuesday by 8 p.m. Central; in 2008, the total was about 525,000 voters. However, the overall turnout, which includes early voting, totaled 368,503, which was the second-lowest turnout in 12 years; in 2012, total turnout was 329,537.

When Emily Ioppolo, a theater production artist, and her boyfriend went to vote at 6 a.m. at a church in their Lakeview neighborhood, on the North Side of Chicago, they encountered empty tables. Precinct workers told them that ballots and machines had not yet been delivered.

The couple returned after 7 a.m. and, once again, nothing was there. “They were trying to call the board of elections but no one was picking up,” she said.

Eventually, Ioppolo, 27, walked to another voting center open to all residents and cast her ballot for Sanders.

“I understand we’re experiencing social distancing right now, but when the governor and the mayor and my alderman say we are still holding elections, it is the board of election’s job to run smoothly,” she said. “It’s not like my polling place was closed down due to a social distancing effort — it was open. That is very frustrating.”

In Palatine, a northwest suburb of Chicago, Kim Inman, 62, said her family urged her not to serve as an election judge this year out of fears of contracting the coronavirus. She decided to go ahead after she received an email from the Cook County Clerk’s Office promising that her location would have hand sanitizer and disinfectant wipes.

When she showed up at 6 a.m., the supplies weren’t there, and they still had not arrived by late morning. Two of the four judges also did not show up, so Inman was left staffing the precinct with only a high school student to help.

“It’s very disappointing,” she said. “This is so unusual and different — I don’t know what’s going on.”

As voting continued haltingly through the morning in some areas, election officials sought to reassure dozens of voters who complained on social media.

Those efforts did not quell the anxiety. Timna Axel, communications director for the Chicago Lawyers’ Committee for Civil Rights, said the group has received an unprecedented volume of calls for a primary election, including an entirely new category of complaint: from confused election workers.

“They’re brand new, substituting for those who canceled,” she said. “We’ve never gotten those calls before on this number.”

Speaking to reporters Tuesday afternoon, Illinois Governor J.B. Pritzker (D) said he offered the Chicago Board of Elections “plains­clothed” personnel from the National Guard as potential election judges and volunteers “should they need it.”

“They did not want that. We offered the opportunity,” he said.

A spokesman for the Chicago Board of Elections did not respond to a request for comment.

The confusion helped incubate online conspiracy theories, as claims of election rigging circulated on Twitter and Facebook.

Some were based on a video showing a CBS affiliate in central Illinois on Monday displaying test results for Tuesday’s election. The 40-second segment, which appeared during “The Price is Right,” was an error resulting from pre-election testing, said Rich Flesch, the news director at WCIA-TV. But a video of the mysterious report, pushed by left- and right-wing accounts alleging election fraud, was viewed nearly 100,000 times.

In Florida, Palm Beach County had some of the worst disruptions in the state, said Liza McClenaghan of Common Cause Florida: By midmorning, some polling places had not opened, some opened late and some were understaffed.

A number of precincts also saw little foot traffic on Tuesday: In the Palm Beach recreation center where President Trump is registered to vote, about 3 miles north of Mar-a-Lago, there were three poll workers, boxes of gloves and canisters of hand wipes, but no voters at midday.

Two deaths in Florida reported Tuesday related to the coronavirus occurred at an assisted living facility that, until last week, was also a polling place in Broward County.

In Arizona, advocates said the closure of municipal buildings to the general public added to voters’ confusion, since a number of polling locations were still operating there.

In Maricopa County, where there appeared to be few issues with the administration of the vote, most early media attention had been focused on officials’ last-minute decision Saturday to close 78 polling locations, citing widespread shortages of cleaning supplies. Voters were instructed to cast ballots at any of 151 geographically dispersed polling centers. That number was reduced to 148 on Tuesday.

Maricopa County Recorder Adrian Fontes said the choices of which locations to consolidate were not made lightly.

“We had a meeting Thursday night, and all of the voices around the table agreed, ‘Look, if we’re going to close some locations, we need to pay very special attention to our communities of color and Native American populations. We need to make sure that we don’t run afoul of any voting rights issues, even though we’re dealing with this global pandemic.’ We don’t use covid-19 to violate voters’ rights,” he said.

Guarino reported from Chicago. Michael Scherer, Felicia Sonmez and Rachel Chason in Washington, Lori Rozsa in Palm Beach, Fla., Joanna Connors in Cleveland, and Holly Bailey and Jimmy Magahern in Phoenix contributed to this report.