We might as well start with David Paterson.
On March 1, 2008, he was the little-known Democratic lieutenant governor of New York, holding a position to which residents of the Empire State generally pay little to no attention. By April 1, though, he was governor, after the sitting executive, Eliot Spitzer, resigned following revelations that he’d paid women for sex. Polling conducted as he took office found that 3-in-10 New Yorkers didn’t know enough about their new governor to have an opinion of him. It’s safe to assume that a decent chunk of the other 7 in 10 were simply pretending they did.