We can speculate about the reason for Trump’s weird mental block on this. Trump supporter Rick Santorum—in the most backhanded defense of Trump I’ve ever seen—attributed it to megalomania: Trump doesn’t like to “say something bad about people who support him.” Another possibility is that Trump has had his thinking influenced by his close advisor Stephen Miller, who has a known affinity for white nationalist websites such as VDARE.

Either reason takes us into dangerous territory, because President Trump spent the last five to ten minutes of the debate declaring mail-in ballots to be inherently fraudulent and laying the predicate to reject the results of November’s election. Such a maneuver could set the country up for months of chaos. And he had—only a few minutes before—told right-wing militias to “stand by” to “do something about the left.”

Trump’s unwillingness to condemn racists and right-wing zealots three years ago in Charlottesville has turned into a persistent pattern—and it is now revealed as part of a larger agenda that marks the ambitions of an aspiring tyrant.