American presidents get the scandals they deserve. Richard Nixon's paranoia produced Watergate. Ronald Reagan's indifference contributed to Iran-contra. Bill Clinton's appetites led to impeachment. And Donald Trump's delusions - about his singular abilities and the impunity of his office - are propelling the crisis of legitimacy threatening his presidency. No matter how distinct presidential scandals appear in their origins, however, there is also a weary sameness to how presidents react to them, how Washington mobilizes for them, how history looms over them.