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Elections officials have stocked up on hand sanitizer and disinfecting wipes. Many are urging voters to cast absentee ballots or vote early to avoid crowds.

But as the coronavirus pandemic worsens, local and state officials are scrambling to identify other options if public health leaders ultimately determine that there are risks to visiting polling places — an assessment that could change the basic mechanics of running an election midstream in a presidential campaign year.

“If you’re talking about something on that level, then we’re clearly facing a crisis and not just an emergency, and public health and safety will have to dictate whatever we do,” said Ohio Secretary of State Frank LaRose, who said he would follow the advice of public health officials and law enforcement.

“One of the very few things that would take precedent over a free and fair election is public health and safety, right?” LaRose said, adding that such a move would be a last resort.

The spiraling covid-19 pandemic that has shaken the global economy and upended millions of Americans’ routines in the past month has emerged in the past week as a unique and unprecedented challenge for elections officials already grappling with a variety of threats such as online disinformation and security vulnerabilities.

While many jurisdictions have emergency plans in cases of natural disasters or power grid failures, there has been little planning for a health pandemic that could keep the public quarantined inside their homes, experts said.

“I don’t think we’ve really considered a scenario like this. I haven’t seen anything on this scope and scale,” said Jennifer Morrell, a former election official in Utah and Colorado and partner with Elections Group, a consulting firm.

For now, health officials have not declared polling sites off-limits. But elections officials in states holding primaries on Tuesday — Ohio, Florida, Arizona and Illinois — are developing on-the-fly contingency plans to mitigate the risks to voters and encourage them to participate.

Hours after Ohio Gov. Mike DeWine (R) declared a state of emergency related to the virus earlier this week, LaRose announced that at least 128 polling places in nursing homes would be relocated. He also ordered county election officials to establish curbside drop-off points for absentee ballots on Election Day and has encouraged young people to enlist as poll workers in the likelihood that older people opt out over health concerns,

“It’s not a time to mince words and sort of dance around the issue,” LaRose said. “You need to be very clear and up front with people and also based in facts, not fear.”

Officials around the country are encouraging early and absentee voting, some of the few immediate options available to the roughly two dozen states that will hold their contests in the upcoming weeks and months.

The need for a plan is already acute in Westchester County, N.Y., where Gov. Andrew M. Cuomo (D) imposed a one-mile containment zone in the city of New Rochelle, the epicenter of the state’s outbreak. People are free to enter and exit, but public gathering places such as schools and houses of worship are required to close for 14 days beginning Thursday.

New York’s presidential primaries are not scheduled to take place until April 28. However, county officials are already discussing what to do if quarantine-like procedures are in place on that date.

Reginald A. LaFayette, a Westchester County election commissioner, said officials are studying the location of polling places inside the containment zone and considering allowing voters who are not showing symptoms to cast ballots as usual. Those who are quarantined inside their homes might need to receive ballots by mail, he said, emphasizing that no final decisions have been made.

“Of course, this is unexpected, so we wouldn’t have had a plan. . . . It’s not a quick fix and not a quick answer,” LaFayette said.

Other countries are grappling with similar issues. In Israel, voters under quarantine cast ballots in the March 2 election using special polling stations, where they were met by trained paramedics in head-to-toe protective gear, according to Israeli media.

Ahead of the U.S. general election in November, some advocates are encouraging states to add expanded mail-in voting to their existing contingency plans as a way to safeguard the franchise in case of an ongoing public health crisis.

On Wednesday, Sen. Ron Wyden (D-Ore.), whose home state has voted entirely by mail since the 1990s, introduced legislation to give Americans the right to vote by mail during a widespread emergency; it would provide states with $500 million to fund the effort.

Yet while voting by mail is seen as an attractive alternative in the face of a public health crisis, some experts said creating and operating such a system on a large scale before November could be difficult in the coming months.

Election administrators would have to contract with the vendors responsible for printing up to thousands of ballot styles, placing them in envelopes and making such each voter receives the correct one. The Postal Service would be burdened in a new way. Officials would have to develop policies to address issues such as nonmatching signatures. Some jurisdictions require mail and absentee voters to provide signatures to verify their identity.

States that have adopted a full vote-by mail system, such as Colorado, took years to progress from no-excuse absentee voting to a permanent absentee list to the full electorate casting ballots by mail.

It is also unclear whether voters would trust such a system if it were rapidly put in place, experts said.

“If you have a pandemic and you require this, I think that’s a little bit of a question mark. Will certain communities respond to that favorably, and trust it and feel confident about it?” Morrell said. “If you talk to my good friends in Massachusetts or somewhere on the East Coast, they’re going to tell you, ‘That’s just not how we do things around here.’ ”

Matthew Weil, director of the Elections Project at the Bipartisan Policy Center, said such a massive mail effort could overwhelm the postal system in the current environment.

“I’m no expert in coronavirus, but if everything is shutting down, I don’t know why we all assume that the mail service is going to be working perfectly,” he said. “One-hundred million ballots through the mail? That’s going to tax the system in the best of times, let alone when we have a pandemic.”

But advocates say they believe some progress toward broader voting by mail is possible this year.

Amber McReynolds, CEO of the National Vote at Home Institute and Coalition, a nonprofit advocacy group, said she is refining a plan for states that wish to ramp up voting by mail before November and are willing to at least temporarily consolidate election operations at the state or regional level. In some states, this could require governors to exercise emergency legal authorities.

“What I’ve basically said is I think we have about a month” for states to make the decision, she said. “It could be May 1, but pretty much within the next month. It would mean hitting ‘go’ and saying, ‘Let’s start a plan to get this infrastructure in production.’ ”

Ohio offers no-excuse absentee voting, but LaRose has advocated for statutory changes allowing voters to enroll online and requiring the state to cover postage costs. Legislative action would be required in many states to change the details of how elections are run.

“I go back to my time in the military, particularly serving in a Special Operations unit. One of the things we learned to do is to be flexible and adapt to emerging threats,” LaRose said.

Kristen Clarke, president and executive director of the Lawyers’ Committee for Civil Rights Under Law, urged election officials to review “unnecessary restrictions” on absentee or mail-in voting in their states.

“Election officials should no doubt be instilling confidence in the electorate right now,” she said on a conference call with reporters during Tuesday’s primaries. “They should not be feeding into anxieties . . . This is an important moment for outreach.”

Weil said the possibility of a coronavirus crisis is uncharted territory for the election administration community.

“Everyone I’ve met and talked to always has a plan for everything, and yet, I don’t think they have a plan for this,” he said. “So everything they’re doing now is reactive. It’s not been proactive.”