WASHINGTON — The script should be familiar by now. President Trump takes action that stuns the country, eliciting indignation and disbelief from Democrats and leading them to conclude that the vitality of American democracy is under assault.

Yet among those who are sympathetic to the president — a minority, to be sure, but somewhere around 40 percent of the country, according to recent polls — the outrage is that Mr. Trump is again being held to an unfair standard set by the very people and institutions that tried to stop his election in the first place: Democrats, resentful Republicans and, perhaps most of all, the news media.

That has certainly been the divide as the country absorbed the news that Mr. Trump had fired James B. Comey as F.B.I. director. The move was widely hailed by conservatives online, on talk radio, on Fox News and among the president’s allies in Washington: the universe in which views of Mr. Trump quickly harden in the right’s collective consciousness.

More clearly than other recent Trump-induced uproars, the reaction to the Comey firing illustrated how many conservatives now justify their defense of the president as part of a fight against a rising tide of overreaction and manufactured hysteria by the left. Mr. Trump, who has long understood the political power of demonizing his opponents as crazed and irrational, has helped stoke those resentments.