Immigration is President Trump’s signature issue, so not surprisingly, he has an immigration solution to the coronavirus pandemic: Stop letting people come to America.

Trump said on April 20 he plans to sign an executive order temporarily banning all legal immigration to the United States, in order to protect American jobs and to help defeat the “invisible enemy” (coronavirus). The logic is specious. Legal immigration benefits the economy because it expands the labor force and generates more economic activity, and there’s scant evidence legal immigrants take jobs that would otherwise go to native-born Americans. And with 2.5 million confirmed coronavirus cases in the world—and probably multiples of that unconfirmed—the virus is already widely prevalent here. Banning new immigration probably won’t reduce infection rates one bit.

No public health experts think banning immigration is an effective way to battle the coronavirus. So why do it? For an obvious, Trumpian reason: To fire up his core supporters, who are generally opposed to immigration.

But Trump’s repeated efforts to appease his so-called base are politically risky, and the issue of immigration illustrates why. A majority of Americans support legal immigration, and acceptance of immigration has actually inched up since Trump won the presidency in 2016. And voters in swing states crucial to Trump’s reelection increasingly tilt against his immigration policies.

“The president is running on a whole lot of issues where he’s out of step with the country, and immigration is the most important,” Democratic pollster Stanley Greenberg said recently on the Yahoo Finance Electionomics podcast. “The president wants to close borders and build the wall, but people think immigration benefits the country. He’s still running as an anti-immigration president.”

Greenberg’s latest polling, from March, shows that 57% of voters in 16 swing states have a “warm” view on immigrants, while just 17% have a “cool” view, for a net positive of 40%. Since Trump’s election in 2016 hinged on narrow victories in swing states like Wisconsin, Michigan and Pennsylvania, a small erosion in support on Trump’s top issue could easily flip such states to Joe Biden, Trump’s likely Democratic rival.

Voters also seem to have softened up on immigration in recent years, even as Trump has remained a hard-liner. The portion of Americans saying the U.S. should have more immigration rose from 21% in 2016 to 27% in 2019, while the portion favoring less immigration fell from 38% to 35%.

Trump highlights illegal immigration more than the legal variety—calling it an “invasion,” at one point. But Trump has tried to limit legal immigration as well, including his attempt to ban Muslims from immigrating to the United States, a reduction in refugee allotments and slowing the green-card process.