Walz’s rhetoric is broadly populist in character. Both parties are populist now—and populism as a movement has always been something of an “empty signifier” that can be filled with any old ideology. But Walz is also making an argument about betrayal, which is how I read it. It’s not (just) that Vance got rich and educated, but that he betrayed his upbringing and own ideals in the process. He didn’t “go back home” so to speak; that’s his sin. But the populist rhetoric comes through clearer and is more salient right now.