Many years ago, after losing a couple of games, University of Texas football coach Darrell Royal was asked whether he would change his approach for the next opponent. “You dance with who brung you,” he replied in his trademark folksy manner. “We’ll keep doing the same things that have worked so well for us through the years.”

Donald Trump waltzed into the presidency with coded but unmistakable appeals to the racial resentments of aggrieved white people. In the middle of the congressional campaign, he is holding on tight to his best dance partner.

As a simple policy matter, it’s hard to see why the president is so worked up about the procession of migrants moving north from Central America. They are more than 1,000 miles away, traveling on foot. Their number, 7,000 or so, is a tiny fraction of the 300,000 people apprehended at the U.S.-Mexico border last year.

These foreigners won’t be hard to spot if and when they get to the Rio Grande — unlike the thousands who try to sneak over. Their apparent goal is to ask for asylum, not to storm across the border. The Mexican border city of Tijuana already has thousands of such migrants sleeping in shelters and on streets, waiting for U.S. immigration officers to get around to screening them.

As for the claim by Trump and others that Middle Eastern terrorists and members of the MS-13 gang are coming in the caravan, a couple of facts stand out. First, he has no evidence. “There’s no proof of anything,” he admitted Tuesday. “But they could very well be.”

A senior counterterrorism official with a tighter grip on reality told CNN, “We do not see any evidence that ISIS or other Sunni terrorist groups are trying to infiltrate the southern U.S. border.”

If you were an Islamic State fighter hoping to come here to slaughter Americans, would you insert yourself into a mass of people practically big enough to be seen from outer space, or might you pay a veteran smuggler to spirit you undetected across the border?

Even if the bad guys chose to trudge a thousand miles, it probably wouldn’t do them any good. Most Central American applicants are denied asylum, and anyone who appears to pose a danger will have an especially hard time qualifying.

But Trump doesn’t let facts hinder his panic-mongering. His falsehoods serve to assure whites with resentments or suspicions against Latinos, blacks, immigrants and Muslims that he is on their side.

It’s often said that Trump won because he appealed to the pain and anxiety of blue-collar Americans harmed by economic change. But the evidence for that belief is lacking, according to the new book “Identity Crisis: The 2016 Presidential Campaign and the Battle for the Meaning of America,” by political scientists John Sides, Michael Tesler and Lynn Vavreck.

Economic anxiety, the authors note, declined under Barack Obama. They found “generally weak relationships” between “measures of economic anxiety and how people voted in 2012 or 2016.” They add, “Changes in household income had little relationship to changes in people’s votes between 2012 and 2016.”

What accounted for Trump’s success? His willingness to appeal directly to voters fearful of groups they see as alien or threatening. “Views of racial inequality, Muslims and immigration, as well as a more politicized white identity, not only were strongly related to whether Americans voted for Clinton or Trump but were also more strongly related to how people voted in 2016 than in other recent presidential elections.”

Trump did much better than Mitt Romney among those who believe whites face a great deal of discrimination and those who have negative views about Muslims. Why? Because Trump made clear to them that he agreed — and Hillary Clinton made clear that she didn’t. (Another factor: “There was unusually strong opposition to Clinton among more sexist men.”)

There are bits of good news in this unsavory picture. First, more people voted for Clinton’s message than Trump’s. Second, the demographic group most receptive to his racialized themes is shrinking. Finally, the public has reacted by becoming more liberal on “race, immigration, Islam and gender,” report Sides, Tesler and Vavreck. “If Trump has moved minds, it has been in the opposite direction from what he intended.”

But his approach worked in 2016. His racially charged pronouncements were music to the ears of many people. And he’s still playing their song.

Steve Chapman, a member of the Tribune Editorial Board, blogs at www.chicagotribune.com/chapman.

schapman@chicagotribune.com

Twitter @SteveChapman13

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