From holding a Bible aloft for a photo op outside a historic church, to scolding NASCAR for banning the Confederate flag at its races, to heralding the “heritage” of the South, Mr. Trump repeatedly elevates to the public stage what he imagines are the top priorities for the voters who back him…

“His intimate connection with the base is one of shared grievance,” Mr. Donovan said. “But when it comes to what they’re for, it inevitably comes off like a cartoon version of what a New York billionaire would think conservatives believe.”…

So far, Mr. Trump has been a durable monument of his own — a testament to the power of negative partisanship as a binding force in modern American politics. But his diminished standing in the polls shows that simply antagonizing the enemies of his loyal supporters may not be enough to help him win.

“He has always been a master at attacking and exploring things people don’t like about his opponents,” said Matt Gorman, a Republican strategist and veteran of past campaigns. “He has to make sure it’s not just about why voters don’t want Biden, but why they want Trump.”