Last week, we gathered with other scholars at Ground Zero for a summit on terrorism and political violence. The mood was somber, not only because of reflections on 9/11 but also because of pained predictions of violence to come. It would have surprised nobody in attendance had they been told another assassination attempt against the former president would occur days later. This was, of course, not merely the second assassination attempt against Donald Trump. There have been many more plots over the past several years — aimed at politicians of all stripes — that never reached the point of gunfire...