This is a great article:
https://apnews.com/article/trump-rhetoric-lies-bully-pulpit-federal-indictment-bb5c99ee151d19085772f8e7c3183fd4
βScholars like me who study presidential rhetoric, presidential communication, they call it essentially a second Constitution,β said Jennifer Mercieca, a communications scholar at Texas A&M University. Having presidents communicate directly to the public βchanged the complete balance and separation of powers without having a new constitutional convention. It made the president the center of our political system.β
Trump, in effect, is arguing that his words as president carried no special force and he was simply exercising his free speech rights.
βMost presidents have a sense of the importance of language β of the written word, of the spoken word,β said Wayne Fields, a professor at Washington University in St. Louis and an expert on presidential rhetoric. βSome of them are not particularly good at it themselves, but they rarely are quite so dismissive of it as Trump has been.β