Yet this is not the only kind of viral pandemic the world has lately confronted. There is, as well, the virus of political extremism. These strains are most active and worrisome on the white supremacist right. According to the Center for Strategic and International Studies in Washington D.C., there have been 267 rightwing plots or attacks in the United States since 2015, leading to more than 90 deaths. Over the past six years, several dozen Black, Islamic and Jewish houses of worship have been the targets of either attacks or plots. “The number of domestic terror plots and attacks,” Seth Jones, the CSIS database director, observed, “are at the highest they have been in decades.”