DES MOINES, Iowa (AP) — In a barn down a gravel road in Iowa, Joe Biden tore into President Donald Trump's moral character, declaring in one of the fiercest speeches of his campaign that the words of the American president matter.

The next day, Biden's own words tripped him up. He told an audience in Des Moines that poor children are "just as bright and just as talented as white kids," before immediately clarifying his remarks.

The back-to-back episodes magnified the promise and the peril of Biden's candidacy. Three months after announcing his White House bid, he remains atop early polling for...