FiveThirtyEight also just published this interesting piece by Bacon along with Julia Azari:

GOP Criticism Of Trump Is All Talk — But It Still Matters, July 23

[....]  the few Republicans in the Senate willing to criticize Trump have mostly done only that, spurring some eye-rolling exasperation from people who want action, not just words. But we think this vein of criticism of Trump-skeptical Republicans is, well, kind of wrong. It ignores the power of words to serve as a reminder that Trump isn’t an entirely normal Republican, and that he doesn’t have complete Republican support — at least, not all the time. It’s true that Flake and other Trump-skeptical Republicans could do much, much more. But that doesn’t mean what they’re doing now is meaningless.

Weakening the impact of Trump’s rhetoric

Political scientists have done a great deal of research to figure out how much the president’s words matter — if they matter at all. Here’s what’s generally agreed upon: Presidential communication matters in a number of important ways. It can shape what issues citizens think about in the first place, how the public views the particular meaning or context of a major event, and provide important cues to partisans about where the party standson a given issue [....]