Voters voiced concerns about the delivery and security of mail ballots as five states held primaries Tuesday, highlighting how the rapid shift to absentee voting during the coronavirus pandemic has emerged as a central issue in this year’s elections.

In Michigan, voters complained that they received their ballots just before Tuesday’s vote or not at all, raising fears that political pressure could be affecting the U.S. Postal Service three months before the Nov. 3 presidential election. In Kansas and Missouri, many conservatives chose to cast ballots in person despite the possible health risk, some echoing President Trump’s unfounded claims that mail voting leads to widespread fraud.

The number of absentee ballot requests broke records in at least two states with primaries on Tuesday, offering further evidence of voters’ embrace of mail voting to avoid potential exposure to the novel coronavirus at polling locations. At least 77 percent of American voters will be able to cast ballots through the mail in the fall, according to a Washington Post tracker of state rules.

Yet the dramatic shift has not always been smooth, with local election administrators struggling to meet demand for absentee ballots with what they describe as a lack of sufficient funding and personnel.

Recent policy changes at the Postal Service put in place by the new postmaster general, a top Trump donor, have caused days-long backlogs of mail, according to postal employees and union officials, heightening fears that some absentee ballots will not be delivered in time to be counted.

The Postal Service has said the changes are aimed at stabilizing the agency after decades of financial problems and not meant to delay ballots, which it has promised to deliver in a timely manner.

But as some Detroit residents reported waiting weeks to receive their absentee ballots, officials and voters said they were worried about how it bodes for the fall.

“I believe there are going to be delays and all kinds of confusion and chaos, depending on where one lives, how informed they are,” said Linda Grissom, 65, who chose to vote in person Tuesday, wearing a blue mask as she cast her ballot at Wayne County Community College on the city’s northwest side.

Claretha Doggan, 70, said she applied for an absentee ballot at the beginning of July but did not receive one until Monday. She decided to drop it off in person at the polling location to make sure it was counted, noting that not everyone has the ability to get to the polls.

“Some people don’t have transportation. So that could be a problem,” said Doggan, who said she hopes she is able to vote by mail in the fall because of her age.

“It didn’t work for me this time,” she said, referring to the wait to receive her ballot.

Requests for absentee ballots have risen around the country this year because of the pandemic, including in Arizona, Kansas and Missouri, which also were holding primaries Tuesday. Voters also cast ballots in Washington state, which has held universal mail elections for nearly a decade.

However, public surveys show a growing divide between Democrats and Republicans about the security of voting by mail, with Republicans saying they are far less likely to trust it in November. Party leaders in several states said they are encountering resistance among GOP voters who are being encouraged to vote absentee while also seeing the president describe mail voting as “rigged” and “fraudulent.”

Trump, who has attacked voting by mail roughly 80 times since late March, has recently intensified his criticism of the Postal Service.

“The post office, for many, many years, has been run in a fashion that hasn’t been great,” the president told reporters Monday. “Great workers and everything, but they have old equipment, very old equipment, and I don’t think the post office is prepared for a thing like this.”

Some Republican voters echoed his comments as they went to the polls Tuesday.

“We don’t have a good mail system. It’s really not viable anymore,” Frederick Thompson, 62, an attorney, said as he voted in Kansas City, Mo. “We have been on a downward spiral with the mail for some time.”

Thompson, a Trump supporter, said he does not think expanded mail-in voting is a good idea because of what he says is a vulnerability to tampering.

“One, there is no accountability,” he said. “There is no degree of certainty it would even work. And two, it is potentially rife for fraud.”

Election officials throughout the country have challenged Trump’s claims that voting by mail will lead to widespread fraud, saying that with the right safeguards, mail voting is secure. Data from several states with all-mail elections show they have had a tiny rate of potentially fraudulent ballots in recent years.

Trump’s message shifted slightly Tuesday, when he urged Floridians to use absentee ballots to vote in November.

“Whether you call it Vote by Mail or Absentee Voting, in Florida the election system is Safe and Secure, Tried and True,” Trump wrote on Twitter. “Florida’s Voting system has been cleaned up (we defeated Democrats attempts at change), so in Florida I encourage all to request a Ballot & Vote by Mail!”

The flood of absentee ballots will delay the primary results in Kansas and Michigan because of the extra time needed to process and count those votes, officials there said — offering a preview of November, when final tallies are expected to take days or even weeks.

In Michigan, which sent out almost 2.1 million absentee ballots for Tuesday’s primary — compared with about 485,000 total ballots cast at the same point in August 2016 — election officials began counting them as soon as the polls opened.

“It’s important from the perspective of the integrity of the elections to try and make sure we have ballots counted in a reasonable time,” said Jake Rollow, a spokesman for Michigan Secretary of State Jocelyn Benson.

As of 6:30 p.m. Tuesday, Michigan voters had returned nearly 1.59 million absentee ballots, breaking the state’s previous record of 1.27 million absentee ballots cast in the November 2016 general election, according to Benson’s office.

In Detroit, where Rep. Rashida Tlaib (D) faced a challenge from Detroit City Council President Brenda Jones on Tuesday, about 90,000 absentee ballots had been issued and 58,000 had been returned as of Saturday, according to City Clerk Janice Winfrey.

At the polling location at Wayne County Community College, where voters were screened for the coronavirus, Annie and Roy Hall said their absentee ballots did not arrive in the mail until Saturday and their daughter did not receive hers until Monday. The couple decided not to risk returning their ballots by mail, choosing instead to drop them off.

“If this works fine, then I’m sure [in November] it will as well,” said Annie Hall, 61.

In a statement Tuesday, Winfrey said the Elections Department had received a “small number of complaints about delayed absentee ballots, which we attribute to mail delays with the Postal Service.”

A spokesperson for the city of Detroit said the city had received a notice from the Postal Service that it could not guarantee delivery of mail-in ballots by Aug. 4.

The USPS said in a July 30 statement to The Post that it planned to send letters to election officials in states that have “deadlines for requesting and casting mail-in ballots” that “appear to be incongruous with the Postal Service’s delivery standards.”

A Detroit-area mail carrier, who spoke on the condition of anonymity because he is not permitted to talk to the media in his job, said he was told by a manager to leave mail behind at processing facilities to adhere to the procedures on delivering late mail. He said that he and his fellow carriers delivered the mail anyway, many of them on their own time.

“We said, ‘It’s election season. Do you see all this political mail? What do you want us to do about that?’ ” the employee said, adding: “The carriers were so outraged about the ballots and the political mail, we said we were still going to take the ballots out. We’re still going to take the political mail out and deliver it.”

A USPS spokesperson responsible for the Detroit area did not respond to a request for comment.

Rollow said Tuesday that his office did not have specific evidence that mail delays would lead to absentee ballots not being counted but that it was safer for voters to drop off their ballots in person. Under Michigan law, ballots must be received by Tuesday night to be counted.

Rollow said the secretary of state’s office has been in frequent communication with the Postal Service and that it redesigned ballot envelopes to make sure they could get delivered as quickly as possible.

“What we’ve been told from USPS is that they, on a daily basis, clear their system of ballots, which are essentially fast-tracked and treated differently than other mail,” he said.

As the after-work rush of voters picked up outside Edison Elementary School on Detroit’s west side Tuesday evening, former state senator Coleman Young II said it was vital that the Postal Service is equipped to handle the unprecedented number of absentee ballots expected in November.

“The post office is more than capable. I think that if we gave them the resources that they were supposed to have, this could be more efficient and effective,” he said. “I think it’s more political in terms of not giving them the resources.”

Meanwhile, there were also reports of long Postal Service delays in Missouri, with mail taking up to 24 days to arrive back at the county election board, compared with up to 10 days in previous years, according to Nancy Miller, co-president of the League of Women Voters of Metro St. Louis.

Statewide, more than 226,000 people in the state had submitted requests for absentee ballots as of Monday — far more than in previous years. Missouri officials relaxed notary requirements for high-risk groups such as the elderly to make it easier for them to cast absentee ballots.

But some elderly voters faced another hurdle: Their ballots were rejected because of an error they made signing their envelopes, Miller said.

The League of Women Voters was deputized by St. Louis County to contact voters whose ballots were rejected and give them an opportunity to visit the county office in person to verify their identities or give them the option to vote in person Tuesday. While hundreds showed up in person in recent days to make sure their votes were counted, not all of those whose ballots were rejected were able to do so, Miller said.

“People who were very old did not drive or did not have a family member available to take them up to remedy whatever they had not done correctly,” she said. “It was very frustrating because you really didn’t have a good solution for them.”

The county is looking into redesigning the ballot envelope to avoid this problem in November, she said.

In Kansas, state law allows ballots postmarked on Election Day to be counted through Friday. Officials will release results starting at 7 p.m. Tuesday — as well as on Wednesday, Thursday and Friday evenings.

“There could be a significant number of ballots received and counted after election day,” the elections board of Johnson County, the state’s most populous, said in a statement.

At Westside Church of the Nazarene in Olathe, Kan., many Republican voters were choosing between the two front-runners to replace retiring Sen. Pat Roberts (R): Rep. Roger Marshall, the establishment pick, and firebrand conservative Kris Kobach, the former Kansas secretary of state who has made fighting election fraud the hallmark of his political career.

Some at the church said they felt that more widespread voting by mail in November would be risky.

“I think mail-in voting is a disaster in the making. There is too much corruption, and we have already seen that in some states,” said Ron Harrison, 70, a retired mechanical engineer and conservative Republican. “It’s silly. There is no reason to do that and open up potential problems. The post office can’t handle that amount of mail.”

But Keri Smith, 47, a nurse and “unhappy Republican,” said she supported mail-in voting, adding, “I’m all for anything that allows more people to vote.” Trump, she said, was “ridiculous.”

Gowen reported from Kansas City, Mo., and Olathe, Kan., and Ruble reported from Detroit. Jacob Bogage, Michelle Ye Hee Lee, Amy Gardner and John Wagner in Washington contributed to this report.