Roberts asks "what if Mueller proves his case and it doesn't matter?":
Say Mueller reveals hard proof that the Trump campaign knowingly colluded with Russia, strategically using leaked emails to hurt Clinton’s campaign. Say the president — backed by the Wall Street Journal editorial page, Fox News, Breitbart, most of the US Cabinet, half the panelists on CNN, most of the radio talk show hosts in the country, and an enormous network of Russian-paid hackers and volunteer shitposters working through social media — rejects the evidence.
They might say Mueller is compromised. It’s a Hillary/Deep State plot. There’s nothing wrong with colluding with Russia in this particular way. Dems did it first. All of the above. Whatever.
Say the entire right-wing media machine kicks to life and dismisses the whole thing as a scam — and conservatives believe them. The conservative base remains committed to Trump, politicians remain scared to cross the base, and US politics remains stuck in partisan paralysis, unable to act on what Mueller discovers.
In short, what if Mueller proves the case and it’s not enough? What if there is no longer any evidentiary standard that could overcome the influence of right-wing media?
The US is experiencing a deep epistemic breach, a split not just in what we value or want, but in who we trust, how we come to know things, and what we believe we know — what we believe exists, is true, has happened and is happening. (Epistemology is the branch of philosophy having to do with how we know things and what it means for something to be true or false, accurate or inaccurate.)
As long as the base is convinced that Mueller is an agent of the deep state (or whatever), it will punish any Republican politician that strays from the pack and criticizes Trump. For a GOP officeholder, standing up for democratic integrity could mean sacrificing reelection in 2018 or 2020.
As long as Republican politicians are frightened by the base, the base is frightened by scary conspiracies in right-wing media, and right-wing media makes more money the more frightened everyone is, Trump appears to be safe. As long as the incentives are aligned in that direction, there will be no substantial movement to censure, restrain, or remove him from office.