Hoping to slow the spread of the coronavirus pandemic, public officials are turning to a controversial tactic: trying to impose rules on interstate travel. Governors in states as different as Hawaii and Rhode Island are requiring Americans coming from states with high rates of the virus to self-quarantine or asking them to not come at all. Florida Gov. Ron DeSantis said he would only allow Floridians — and not other U.S. citizens — to get off docking cruise ships. Mayors near Cleveland are asking snowbirds not to return from Florida. Even President Trump suggested quarantining the New York, New Jersey and Connecticut tri-state area.

Efforts to “flatten the curve” — reducing strain on health services through social distancing and by isolating where possible — put state governors in a peculiar collective action problem. What do they do when other states are not following the recommended practices?

Governors in New York, California and Washington state have been on the forefront, closing state parks, playgrounds, schools and encouraging citizens to stay at home — although New York City, with its exceptionally close living conditions, has been hit hard nevertheless. Meanwhile, despite Centers for Disease Control and Prevention recommendations to halt large gatherings, spring breakers flocked en masse to the beaches of Fort Lauderdale, Fla.; though DeSantis ignored the recommendations, some local officials closed beaches anyway. In New Orleans, Mardi Gras continued as scheduled. Across the United States, states and local areas have varied widely on whether and what restrictions they’ve issued on travel, businesses and public gatherings.

But even where governors issue strong restrictions — closing restaurants, bars, playgrounds and other public gathering places — neighboring states may not. For instance, Louisiana has issued a statewide stay-at-home order, but bordering states including Alabama and Texas have not. So what’s a governor to do?

What the public thinks of border closings within U.S.

Americans are fairly evenly divided on whether closing state borders is acceptable, my research with collaborators finds. From March 20 to 23, political scientists Shana Kushner Gadarian, Tom Pepinsky and I surveyed 3,000 Americans in a nationally representative survey administered by YouGov. We asked, “Do you agree or disagree the United States should impose a domestic travel ban between U.S. states?” Respondents answered on a five-point scale. As you can see in the figure below, respondents’ agreement and disagreement are evenly distributed: Roughly as many people strongly or somewhat agree (38.5 percent) as strongly or somewhat disagree (37.7 percent). And 23.9 percent neither agree or disagree.

These differences in opinion do not seem to divide by party. As the figure below shows, both Republicans and Democrats exhibit a similar level of agreement and disagreement when it comes to banning interstate travel. While Republicans appear evenly divided between agreement and disagreement, Democrats exhibit higher levels of agreement (41 percent, combining strong and somewhat agreement) than disagreement (36 percent). Though, for individuals who do not identify as Republican or Democrat, we can see a stronger trend against imposing domestic travel bans.

Opinion is evenly distributed, and with no strong preference yet by party identity. This suggests people don’t yet have strong opinions. If political leaders wanted, they could muster mass support for or against closing interstate borders, imposing highway temperature checks, or otherwise limiting travel. Governors could impose laws with popular support even if they had undemocratic and illiberal implications.

Border closings in Europe

We could compare the United States with how individual European governments have been relating to the European Union. Twenty-six European countries are in the Schengen Area, which permits people to move freely among the member countries. However, unlike U.S. states, each of these 26 governments can introduce border controls in emergencies, which many did during Europe’s 2015 refugee crisis. As covid-19 spread in Italy, European leaders initially balked at suspending free movement. But as Italy’s situation worsened, one by one, Germany, Spain, Switzerland and others began to shut down borders, with exceptions for commercial traffic.

In Europe, free movement is not just a right but also a symbol of European solidarity and identity. These symbols are important. Keeping the Schengen area in place was one reason German Chancellor Angela Merkel gave for keeping borders open as Italy’s crisis escalated.

Since health and immigration are considered issues of national security, European governments have largely paved their own paths, gradually converging on travel restrictions and stay-at-home measures, as each government tried to halt the pandemic’s spread. Some governments are taking a different approach: relying not on government edicts but on high social trust to ask their citizens and visitors to reduce travel, self-quarantine if they have symptoms, and stay at a distance from one another. Overall, the E.U. has been criticized for its slow response and fumbling leadership, leaving countries to proceed on their own.

The U.S. states find themselves in a similar situation, with no clear federal leadership. The Trump administration has been undercutting the CDC messaging and using politics to make public health decisions. Trump has told U.S. governors to take matters into their own hands, often leading to bidding wars with other states for supplies.

Why should governors keep borders open? For one, openness allows different governments to mobilize together and coordinate public health resources. The states have extremely varying levels of hospital beds, tests, ventilators and other health-care necessities. That’s also true in Europe, a second reason Merkel originally wanted to keep borders open, enabling German hospitals to treat Italian patients, for example. And keeping borders open prevents cross-border panic-buying.

When trying to contain a pandemic, border closures are essential. But when trying instead to mitigate its effects, the decision to do so is more difficult — and more political. Flattening the curve through social distancing only works with cooperation. For this, citizens take their cues from political leaders and health experts.

Our research shows citizens do not have strong preferences on border closure and can therefore be persuaded by effective messaging. A lack of consistent messaging from the federal government or central leadership — especially when it actually encourages competition instead of cooperation — suggests a deeper problem: a lack of national solidarity.

Sara Wallace Goodman (@ThatSaraGoodman) is an associate professor of political science at the University of California at Irvine.