Americans have long been practicing social distancing when it comes to their politics.

While health officials search for a vaccine to combat the novel coronavirus, we need to find a vaccine for toxic partisanship.

Because, at a moment when the United States needs to come together to combat a common enemy, the virus itself has become yet another way to glimpse our cavernous divide.

We’ve all been told to practice self-isolation, work from home if possible and wash our hands as if grandma’s life depended on it. But whether you fully embrace these steps depends on your politics: According to a new Pew Research Center study, almost 50 percent of Democrats and Democratic-leaning independents say the outbreak is a major threat to the population. Only 33 percent of Republicans and independents who lean toward the GOP agree.

Pew’s studies often find that our view of national problems is shaped by our politics, but this widely disparate take is far more consequential. This one really matters: Differing attitudes may determine how people respond to the health crisis in their own lives and homes; whether enough people follow the public health advice may determine whether the nation as a whole can combat a deadly pathogen and save lives.

But not everyone sees the threat. Just as President Trump was declaring a national emergency at the end of last week, an NBC-Wall Street Journal poll surveyed registered voters and found their reaction to the covid-19 virus may make a unified national response impossible. More than 8 in 10 registered Democrats in the NBC-WSJ poll were highly critical of the president’s handling of the crisis, while 9 in 10 registered Republicans approved. Just 30 percent of Republicans in that survey said they had planned to stop attending large public gatherings. “The problem for us right now is that we are a nation of tribes,” said pollster Peter D. Hart, whose firm conducted the survey.

The partisan divide is so wide you’d think we lived on two different planets. Republicans, in general, said the coronavirus was exaggerated and instead focused their ire at the media with comments such as: “I think this whole coronavirus is way overblown.” And: “Hopefully it will just be over soon or whatever. It will not be such an epidemic.” And a lot of this: “The media … is trying to scare everybody in the country. We’ve had the flu before.”

Democrats blasted the White House for slow action and poor leadership. Among the responses: “They waited to test people because they didn’t want the economy to suffer.” And: “The president doesn’t know what he is doing.” And: “The response is so bad, and they’re endangering lives.”

This virus did not erase our tribal instincts, it amplified them.

But now we face a common enemy without a common set of facts, and that gives a clear advantage to our viral foe. This virus isn’t particular about who thinks what. It doesn’t check at the door to see who plans to vote for Trump or Joe Biden. It doesn’t just contaminate the doorknobs and stair railings of red America or blue America. This is a virus that reaches across borders and continents, its impact varying from one country to the next based on testing levels, the general health of the population and the quality of information that shapes public response.

The most important daily messaging about the pandemic flows from the White House, where the president spent weeks playing down the threat, saying things like, “We pretty much shut it down coming in from China,” or “One day, it’s like a miracle, it will disappear.” Is it any surprise that people were underwhelmed by the threat if they were listening to that?

This was the week that began to change. Fox News is now warning viewers about the threat. The president shifted his message, if not his tone. “I’ve always known this is a real, this is a pandemic,” he said. “I felt it was a pandemic long before it was called a pandemic.” History will adjudicate that claim.

What matters most right now is for everyone, including the president, to use their platforms to get through to people who are still suspect about the threat. Those who believe it’s little more than just the flu. Those who are still flocking to beaches and spring break parties. And those who are already experiencing quarantine fatigue.

Decades from now, people will still be debating whether this president met crucial tests of leadership. But, by one key measure, he nailed it. In order to be a leader, you must have followers. Trump certainly does, and they are avid. They overlook his failures, emulate his tone and echo his language.

So, Mr. President, please think carefully about what you say.

Your words are contagious.

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