Mr. Trump, whose myriad false statements and public lies have been extensively cataloged, hardly caused this phenomenon by himself, but he exemplifies it better than anyone else. He is the Rorschach test of truth, the guidepost by which people choose their story line. Most Americans tell pollsters that they do not believe what he says, but a significant minority considers him a truth-teller in a broader sense, saying out loud what others will not about a broken system he vows to fix, even if he does not hew to particular facts.

And in some ways, his what-you-see-is-what-you-get approach makes him more transparent about his motives and feelings than any president in generations. Rather than hide his more base reactions and ambitions, however raw and unseemly, he flaunts them and invites his supporters to share them.

With the help of social media, friendly news outlets and congressional Republicans willing to follow his lead, he crafts a message that finds its audience.

He took office at a time when trust was already a dwindling commodity in American life. Much of the public may not trust Mr. Trump, according to surveys, but it likewise does not trust his opponents all that much either — or the news media that he complains is out to get him. Americans have been down on banks, big business, the criminal justice system and the health care system for years, and fewer have confidence in churches or organized religion now than at any point since Gallup started asking in 1973.