Donald Trump is old. Were he to be elected president and fail to complete his term, his pick for vice president, Ohio U.S. Sen. JD Vance, would succeed him. Vance is only 40 years old. According to an official biography, after his 18th birthday, Vance spent the next four years in the Marines, the next two years in college, then four years in law school, followed by a year as a law clerk, two years at a law firm, two years at a venture capitalist firm, two years organizing a failed anti-opioid non-profit, and as a senator starting in 2023. Vance has no administrative experience. His longest emp…