If the coronavirus spreads throughout the United States, he said, “We’re going to go through a period, obviously, where public health officials and experts are going to say no shaking hands, no public contact … We may be witnessing an era where television, or more so, social media, becomes the means to campaign in a coronavirus world.”

To most campaign observers, the likelihood of any widespread disruption of the primary remains dim. But if the virus does spread, the mechanical implications for campaigns could be profound.

In the case of an outbreak, said Boyd Brown, a former South Carolina lawmaker and former Democratic National Committee member, “It’s going to be tough. I’m watching [TV] right now and they’re stoking fears, they’re coming live from face mask manufacturing facilities.”

Reaching for an image, Brown, who helped Beto O’Rourke before he abandoned his presidential run, compared the prospect of a coronavirus-afflicted primary to a barren landscape, “very much like the last couple of weeks of the Beto campaign.”

For now, the coronavirus has been felt most severely in the United States in the financial markets and as a point of political positioning, with Democrats criticizing President Donald Trump for his handling of the crisis in recent days.

In South Carolina this week, Mike Bloomberg said the “stock market’s falling apart because people are really worried, and they should be.” Joe Biden pointed to his experience helping respond to the Ebola epidemic, while Elizabeth Warren accused the White House of “absolutely bungling” its response to the disease.

Amy Klobuchar urged Americans to visit the Centers for Disease Control and Prevention website “because many doctors are saying it’s just a matter of time before we’re going to start seeing this here.” At a breakfast in South Carolina on Friday, Bernie Sanders ripped into Trump, saying that instead of campaigning in the state, he should “worry about the coronavirus rather than disrupting the Democratic primary right here in South Carolina.”

The Trump administration’s response to the emergency has been uneven. Robert Redfield, director of the CDC, told lawmakers that the risk to Americans of coronavirus remains low. But CDC officials have also urged Americans to “prepare for the expectation that this might be bad,” including the possibility of child care centers or schools closing.

On Friday, the World Health Organization raised its global risk assessment of coronavirus to its highest level, “very high.”

“There are a whole lot of questions about whether this is going to be enduring or not,” said Bill Carrick, a Democratic strategist who managed Missouri Rep. Dick Gephardt’s 1988 presidential campaign. “If it is enduring," he added, "It could affect rallies. It also could affect travel.”

If the coronavirus does spread during the primary season, its logistical effects could be more painful for some candidates than others. The inability to hold rallies could hurt candidates with less money, such as Biden, who rely more on free media.

That might not hurt a candidate such as Bloomberg, “whose campaign rallies can be a 30-second campaign ad,” said Bob Shrum, a longtime political strategist who served on multiple Democratic presidential campaigns.

Trump could rise or fall on his handling of the crisis, too. In addition to the political calculations — a Morning Consult survey this week found 56 percent of voters approve of his handling of the outbreak, down 5 percentage points from earlier this month — there are his rallies to consider. They are massive and form the identity of his campaign.

Doug Herman, who was a lead mail strategist for Barack Obama’s 2008 and 2012 campaigns, suggested the Democratic candidates’ response to the coronavirus so far has been a missed opportunity. Trump, he said, left a wide opening with his handling of the outbreak, requiring the Democratic candidates to be more assertive on the issue.

So far, he said, they haven’t “cracked much beyond a paragraph of thought on it.”

“There’s a thread here with Trump’s cuts and destroying the credibility of the institutions and the media and the scientists in our government — and now all of a sudden we’re supposed to believe Trump, the government advocate, on this?” Herman said.

Functionally, he said the effects of the coronavirus will not materialize in the campaign unless the outbreak impacts “our gatherings, and our day-to-day lives. Only until that happens — when they won’t go to a restaurant, they won’t go to a mall, they won’t send their kids to school — of course it will have an impact.”

Short of that, said Antjuan Seawright, a South Carolina-based Democratic strategist, a spreading virus would “put a limit on the types of public interaction that people have at events and rallies and people showing up.”

And he said there is little that campaigns can do. “Think about it. I mean, they can’t test people as they come into the rally,” he said.

Still, Seawright is taking one measure himself. When he boards his next flight, he said, “I’m definitely going to put on a mask.”

Holly Otterbein contributed to this report.