President Trump’s short-lived family separation policy extended the hard line on immigration he promoted during his presidential campaign. Many analysts believe that this strategy helped him win the election by politicizing latent nativist sentiment among white Americans. At his rallies, Mr. Trump consistently propounded a view of immigrants as criminals and miscreants, not to mention a cause of unemployment and wage stagnation among native-born citizens. As president, he has continued to use dehumanizing language in reference to immigrants, words like “vermin,” “infest” and “animals.” On Sunday, he dared Democrats to push for the abolition of the Immigration, Customs and Enforcement agency, claiming that if they pursued the idea, they would “never win another election.”

But is it true that immigration is always a losing issue for Democrats? There is a consensus among scholars and commentators that an individual’s view on immigration had a bigger impact on how he or she voted in 2016, compared with recent elections. Given that white Americans tend to be substantially more anti-immigration than pro-immigration, one might expect that highlighting a hard-line stand on the issue would have benefited Mr. Trump in the election.

Contrary to received wisdom, however, the immigration issue did not play to Mr. Trump’s advantage nearly as much as commonly believed. According to our analysis of national survey data from the American National Election Studies (a large, representative sample of the population of the United States), Hillary Clinton did better in the election than she would have if immigration had not been so prominent an issue. In fact, a liberal backlash seems to have contributed to Mrs. Clinton’s victory in the popular vote count.