From an article by Paul Waldman, in The Week, December 6, 2017.
Quoting Billy Bush: When “I called him out for inflating his ratings” on The Apprentice, the future president replied, “People will just believe you. You just tell them and they believe you.”
At that moment, it might have seemed like the sentiment of an amoral sociopath, one who had learned from long experience that if you’re rich enough and brazen enough, you can get away with behavior that ordinary people feel qualms about. But it would also turn out to be a profound insight into contemporary politics, one that the Republican Party has now adopted as one of its fundamental principles.
Not that the GOP was afraid to lie before it raised Trump up as its champion. But they’ve decided that they really can say anything, no matter how ridiculous, obviously false, or morally repellent it might be. People — or at least some people — will just believe them, and even change their own beliefs to match those of their political leaders.
...
There’s no point in even trying to make your argument persuasive, because persuading people who might not already be with you isn’t really the point. All you have to [do] is signal to your partisans: This is what we’re saying now, and yes I know it’s ridiculous, but just say it.
[Boldface added.]
The article also supplies examples. Note, this was three years ago.
https://theweek.com/articles/741495/trumps-unintentionally-profound-insight-into-american-politics