By the late 20th century, “presidential” had become entirely bound up in technological savvy, and Reagan, as could be expected from a former president of the Screen Actors Guild, was an artist when it came to optics. Brian Balogh, a professor at UVA’s Miller Center and co-host of the radio show “BackStory With the American History Guys,” told me that “Reagan’s stroke of genius was to continue running against the establishment while he was actually the president.”