It is often observed among scholars of democracy that an essential ingredient for the success of democracy is for political opponents to view each other, not as implacable enemies to be crushed, but instead as fellow citizens who have good-faith disagreements about what policies government should adopt. There needs to be a sense of a shared enterprise–we are all in this together, undertaking our mutual effort at collective self-government.

There are different ways to express this essential idea. Richard Hofstadter made it a core theme of his important book The Idea of a Party System, where he traces the development of the concept of a “legitimate opposition” in an ongoing electoral competition for temporary control of government power. More poetically, Lincoln in his first inaugural pleaded: “We are not enemies, but friends. We must not be enemies. Though passion may have strained, it must not break our bonds of affection.” More recently, Steven Levisky and Daniel Ziblatt invoked the same principle, as have Lee Drutman and Ezra Klein, among others.

That’s why it was so jarring (at least for me), even after all the increased vitriol of contemporary partisan politics, to hear President Trump at the memorial service for Charlie Kirk snarl (and I believe that’s the correct verb for it): “I hate my opponent, and I don’t want the best for them. I’m sorry. I am sorry, Erika. … But I can’t stand my opponent.” (The quoted words come at about one minute into the video clip; you can judge for yourself President Trump’s tone of voice.)

Democracy does not require the kind of supererogatory forgiveness that Erika Kirk bestowed upon her husband’s assassin, remarkable, moving, and exemplary as it was. But democracy does require that we all–including, and perhaps especially, our elected leaders–treat political opponents as fellow citizens, equally worthy to participate in our shared self-government. The kind of hatred that President Trump expressed is, I fear, fundamentally inconsistent with that elementary level of civic fellowship that is necessary to sustain democracy.