Podiums get sanitized before the candidate steps up to speak. Fist or elbow bumps take the place of handshakes, and kissing babies is out of the question. Rallies are canceled, leaving candidates speaking to a handful of journalists and staffers instead of cheering crowds of thousands.

This is campaigning in the age of the coronavirus, when fears of the new pandemic’s rapid spread are upending Joe Biden’s and Bernie Sanders’ campaigns. The urgency of the issue comes at a pivotal time in the Democratic presidential primary, as Biden is beginning to pull ahead as a front-runner for the nomination and as Sanders is scrambling to catch up.

Biden canceled rallies in Chicago and Miami and is instead planning a series of virtual rallies, details of which have not yet been released.

Biden and Sanders canceled rallies Tuesday night over fears from local officials about holding large indoor gatherings.

The last two major Democratic White House candidates will debate one-on-one Sunday night in Arizona, site of one of the nation’s next round of primary elections March 17.

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The Democratic National Committee and CNN, which is hosting the debate, said the precautions are being taken in the wake of the coronavirus.

“DNC has been in regular communication with local health officials and the mayor's office, which advised that we could proceed as planned,” said DNC Communications Director Xochitl Hinojosa. “Nevertheless, our No. 1 priority has and will continue to be the safety of our staff, campaigns, Arizonans and all those involved in the debate. We will continue to remain in daily contact with all stakeholders through Sunday.”

CNN said its network officials agreed. The debate will air exclusively on CNN, CNN en Español, CNN International and Univision at 8 p.m.

Biden was the big winner in the most recent set of presidential primaries Tuesday night, winning delegate-rich Michigan as well as Missouri, Mississippi and Idaho.

»March 10, 2020, presidential primary results

On Wednesday, Sanders said he was remaining in the race.

“If coronavirus has the lasting impact that we all fear it will, it will also dramatically reshape the way a presidential campaign unfolds,” said Jesse Ferguson, a veteran Democratic strategist and former spokesman for Hillary Clinton”s campaign.

“Politics is fundamentally about leaders interacting with the people who they represent, and if a pandemic forecloses that ability, it changes everything — how you campaign, how you knock on doors, how you do events and how you do the retail part of politics.”

While coronavirus concerns have been building as new cases crop up daily and as Democrats criticize President Donald Trump for what they consider a lackluster response, Tuesday marked the first moment the issue affected the campaigns in a substantive way.

»Delegate tracker for election 2020

Biden delivered a victory speech to a crowd almost entirely composed of media and dozens of staffers who had wandered over from headquarters. It was hardly the big celebration Biden had hoped for on one of the biggest nights of his 2020 campaign.

It’s not the first time a major national crisis has upended the contours of a presidential race. During the 2008 campaign, as the economy was in a free-fall, Republican nominee John McCain returned to Washington to work on the congressional response to the crisis in an effort to revive his flagging campaign.

Steve Schmidt, McCain’s top adviser, has said the coronavirus crisis could be particularly problematic for Sanders — and for Trump.

“The raw politics of this is that it freezes the Democratic race in place for Bernie Sanders, who is on his last legs. You can’t have a revolution without rallies,” he said.

Trump toured the facility with CDC director Robert Redfield. Joining the two were Gov. Brian Kemp, Sens. David Perdue and Kelly Loeffler and Rep. Doug Collins.

Trump, meanwhile, delights in turning out tens of thousands of supporters to his events and has kept up a steady calendar of rallies in recent months.

“The Trump show is sustained by rallies,” he said.

While they have not said they are holding off on rallies, Trump’s campaign doesn’t have any on the schedule — a rare break to his persistent counterprogramming.

The campaign postponed a “Women for Trump” bus tour through Michigan, citing “scheduling conflicts,” after the husband of a participant came into contact with someone who tested positive for the virus at the Conservative Political Action Conference in Washington.

Late Wednesday, the White House announced Trump would cancel his trips to Colorado and Nevada “out of an abundance of caution” amid the coronavirus outbreak. He was set to leave Thursday for a Western swing that would include a pair of fundraisers and an appearance at the annual gathering of the Republican Jewish Coalition in Las Vegas — just the kind of event that public health officials had been urging people to avoid.

The 73-year-old president has also continued to shake hands and speak at large gatherings, despite public health warnings directed at people his age.

While Trump continues his handshaking, those warnings from officials could affect the way Biden campaigns. While the former vice president typically holds smaller events and has only consistently turned out crowds in the thousands since winning South Carolina on Feb. 29, he’s known for his personal, often-physical interactions with voters. He often doles out hugs or goes forehead-to-forehead with a voter to share an emotional moment.

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Rick Hasen, an election law expert and professor at the University of California’s Irvine School of Law, joked that Biden may have “some things to learn about social distancing.”

Election officials in Ohio and Chicago announced they’re moving polling centers out of senior centers and nursing homes, which could make it tougher for seniors to vote and create confusion for voters.

Some Democratic operatives have expressed concerns that some states could see a shortage in volunteers on Election Day. Election officials in Florida, where early voting is underway, are sanitizing voting machines hourly with disinfectant wipes.

Kelly Dietrich, CEO of the National Democratic Training Committee, a group that trains Democrats who want to run for office or work on a campaign, said they’re already seeing a decline in people who have registered to participate in their training over fear of showing up to large gatherings.

“That fear is a prime motivator. It’s going to affect your campaign. It needs to be taken into account,” Dietrich added.

The Associated Press contributed to this report.