Donald Trump wasn’t happy to hear that Bruce Springsteen hasn’t backed down from calling him an “unfit president” as he performs in Europe, so he went on another rant on social media overnight Sunday, demanding a “major” investigation be launched against the rock ‘n’ roll legend for singing at a Kamala Harris rally in October.

Representatives of several of the entertainers targeted by Trump − all of whom have previously endorsed Democratic candidates for president − rejected rumors that they were paid for their endorsements...