Vance’s investigation, which appears to be focussed largely on business practices that Trump engaged in before taking office, may seem picayune in comparison with the outrageous offenses to democratic norms that Trump committed as President. But the New York University historian Ruth Ben-Ghiat, whose recent book “Strongmen” examines the characteristics of antidemocratic rulers, told me, “If you don’t prosecute Trump, it sends the message that all that he did was acceptable.” She pointed out that strongmen typically “inhabit a gray zone between illegal and legal for years”; corrupt acts of political power are just an extension of their shady business practices. “Trumpism isn’t just about him,” Ben-Ghiat went on. “It’s a whole way of being in the world. It’s about secrecy, domination, trickery, and fraud.” She said, of Vance’s probe, “It’s symbolic for the public, and very important to give the public a sense of accountability.”