This leads us to the significant difference between Mr. Wallace and Mr. Trump. Mr. Wallace’s targets were, for the most part, presented in the abstract. Though he denounced broad categories of generic enemies — “agitators,” “anarchists” and “communists” — he rarely went after an individual by name.

Mr. Trump, in pointed contrast, has used his rallies to single out specific enemies. During the 2016 campaign, he demonized his political opponents in the primaries and the general election, and also denounced private individuals, from Megyn Kelly, the former Fox News anchor, to the former Miss Universe Alicia Machado and the federal judge Gonzalo Curiel…

Participants at Mr. Trump’s rallies have been moved to attack individuals he’s singled out. For most rally participants, the attacks have been confined to ominous but nevertheless nonviolent chants — from the 2016 cries of “Lock her up!” to the recent refrain of “Send her back!” But a handful have gone further, targeting the individuals named by the president with death threats and even attempts at violence.

In late 2018, a Trump supporter, Cesar Sayoc Jr., mailed pipe bombs to high-profile Democrats and media figures who had criticized the president and whom the president had denounced in return.