So, overall, I'm not sure what the impact of this, and what Galli's desired outcome is.
Conservative evangelicals are already rejecting this editorial in droves. This won't change anybody's mind on the right.
Why is he writing this? For one, he is retiring in a month (I understand), so he probably has nothing to loose.
He seems to be primarily concerned with the reputation of evangelicals. I don't know what note CT has struck previously, but even if it's a "we Christians don't get involved in politics" note, I think that's wrong. In a democracy, what the government does is supposed to be at the will of the people. The government cannot be irrelevant because it is an extension of the people. Even if it weren't, the job of the prophet is to speak truth to power, not to take care to ensure that he or she is righteous individually.
So, it seems like damage control.
But also: if he gets what he wants (which seems to be impeachment and removal as opposed to losing an election), then Pence becomes President and he runs for reelection (presumably) without Trump's baggage.
I am coming to believe that racism and sexism are what are governing our times these days, not "economic anxiety". The Republicans' coded messages are speaking to that, and whether it's Pence or Trump probably won't make any difference (actually, conservatives would probably prefer their desires weren't so clear, so they might prefer Pence to Trump).