Some thinking out loud.
I just saw a clip of George Will saying the country decided not to remove Clinton from office for his "abominable" behavior because they determined that his crimes were not serious enough to overturn a presidential election. As far as the Cohen stuff is concerned, I'm inclined to say Trump's behavior similarly fails to meet that otherwise reasonable threshold (even if Trump funneled payments through his fake charity).
Could the Daniels/McDougal revelations themselves have turned the election? It's tempting to answer "no" and argue "everyone knew" Trump was a womanizer. Putting aside hindsight bias, the news would have made his cheating more concrete and less abstract. The Access Hollywood tape was "just locker room talk," whereas an affair with a pornstar, and a newborn at home, is pretty scuzzy. The bigger problem could have been, "What else has he done? What else do we not know?"
Trump's narrow victory complicates matters. Overturning an election is serious business, which is why Comey has said the American people should not count on Mueller to save them. Citizens can take matters into their own hands by voting. The argument see-saws the other way because elections derive their moral legitimacy from the will of the people, and we have an Electoral College that awarded the presidency to someone who won fewer votes. It's a stupid institution, but we have to abide by the results (and work to abolish it).
Trump apologists have recently taken to crediting broad powers to the president -- he cannot obstruct justice, he can pardon himself, he's not accountable to financial conflicts of interest; maybe we don't even like it, they could say, but that's how the Constitution works. And if we take that logic, then Congress can impeach and remove the president for just about any ol' reason -- because that's how it works. However, in addition to laws, we have norms and traditions (e.g., release your tax returns) which Trump has been subverting. Even with removing a president, the Constitution undermines popular will; understandably, it requires a super-majority of two-thirds, but that's two-thirds of the highly unrepresentative Senate. Some of these problems are ultimately rooted in a pre-democratic Constitution.
What if Trump won 70% of the vote? Would this Russian probe matter as much? MAGAns would probably say the Democrats are just out to get the president by any means available. Nixon trounced the Democrats in his re-election, yet he was threatened with removal. Corruption, as Biden might say, is a big ******' deal. For the point against, however, there was no recourse available for the people; Nixon was serving his second and final term, so Congress had to use its impeachment power.
I'd bet a lot of people feel the same way -- you can't deny Trump the presidency for a sex scandal, especially if you frame it as a campaign finance violation (and tack on conspiracy for good measure). Now, collaborating with Russia is another matter, and if Mueller can back it up, then I think that's something a large part of the country can get behind.
