I'm still a Never-Trumper, but I favor rejecting him at the polls over impeaching him in Congress. (Ideally, I’d have Congress impeach him next November, after he loses the election, just to denounce him and disqualify him for future office.)
Alleging corrupt intent is too easy and too tempting.
One strong argument against impeachment was made just this morning by Sen. Rand Paul in an interview with Jake Tapper: If your rival’s son robs a liquor store, can you be impeached for demanding he be investigated? Note that I said “impeached,” not “criticized.” A good president would react to news that his rival’s kid is a criminal with “The Justice Department is handling that, and I don’t want to comment on it.” But we don’t have a good president. We have a godawful president. Still, the sin of demanding an investigation of a real crime is way closer to “maladministration” — being a godawful president — than to high crimes and misdemeanors.
So the Dems must fall back to the specifics of the Trump/Biden case. We all know that Trump was not really interested in the Bidens’ corruption, because we all know that he is a corrupt individual who believes in corruption as a way of getting things done. But we can’t impeach him for being a horrible human being, something we knew in 2016. Nor should we take official action against him based on what “we all know,” because we all can come to “know” a lot of things that aren’t true.
I am not saying that we lack evidence that Trump’s motives in the Ukraine affair were electoral. My problem is that I cannot find a bright enough line between what Trump did and what he would have been doing if the Bidens were in fact worthy of investigation (whether or not actually guilty of anything). Too much of the Dems’ case depends on the claim “There is no evidence that Joe ever acted to favor Burisma.” When did the absence of evidence become evidence of absence? Absence of evidence is, indeed, the core of Trump’s weakest defense. We have been subjected to hours of baloney about his not explicitly stating that the aid to Ukraine was contingent on the investigations he was demanding. How can the Dems complain about that defense when their “proof” that Trump’s motive was corrupt is that “there is no evidence” that the Bidens were corrupt?
Maybe that’s why we hear so much about foreign involvement, with continual references to the mention of foreign intrigue in the Federalist. But the argument is circular. The Dems say that Trump is seeking political assistance from Ukraine. Trump says he is demanding help with uncovering American corruption. We have cooperative intelligence arrangements with foreign governments. Australia tipped us off to Russian meddling. That information had positive, but not dispositive(!), political effects for Sec. Clinton. So getting help from foreign powers in matters that have political ramifications is not an impeachable offense. No, it comes back to the fact that Trump is a lying SOB. But all politicians are allegedly lying SOBs. In this case, the allegation of lying is supported only by the absence of evidence that the alleged lie (viz. that the Bidens are corrupt) is true. That's an evidentiary hole that leads, in my view, straight to the voting booth.
Politics ain't beanbag
I carry a very strong presumption in favor of the voters being the ones to punish political chicanery. In a democracy, everything a leader does should have political consequences, and everything a leader does should take into account the extent to which public opinion will favor or condemn it. The matter is subtle: leaders must lead, but they must not coerce. We are seeing this issue play out with healthcare. We know the system is broken, but we are not ready for Medicare for all. If Sen. Warren changes her position on M4A to reassure union workers that they will not be forced to give up their plans, that may sound like opportunism to some, but it sounds like “listening” to others. Who’s to say that the politics did not change her mind about the best policy to pursue? Answer: the voters. NOT the Congress of the United States.
Getting re-elected is what politicians do. News accounts of the machinations relating to impeachment never fail to mention their political ramifications. The GOP is concerned with protecting its vulnerable senators, and the Dems are concerned with protecting their vulnerable representatives. Are these people’s exercise of their public responsibilities not being affected by their political self-interest? How is that different in kind from what they are accusing Trump of doing?
Was Mulvaney wrong? Do we not do “it” all the time? Yes, Mulvaney was “admitting” that there was a quid pro quo for releasing the Ukrainian aid, but that still leaves the “we do it all the time” argument on its own merits. It’s a different argument from the one Trump first made, but it may still be a good argument, and the Dems who are calibrating their  impeachment moves with their political fates in mind are having a hard time refuting it. If it’s so bad to trade foreign aid for political favors, what do we think of basing impeachment decisions on political effects? Has the left wing not “extorted” an impeachment process out of Speaker Pelosi by threatening her speakership? Should they all be “impeached”?
I believe that we must be leery of prosecuting "political" crimes criminally or by impeachment. Trump certainly sought to extort a political favor from Ukraine, with no benefit to the USA. But given a system of government in which political gain (i.e., public approval) of one’s official decisions is at least relevant to most such decisions, a president seeking to “steal” an election by coercing a foreign government to help him slime a rival does not in my judgment rise to the level of high crimes and misdemeanors. This is especially true when, as here, the voters will in fact get to vote on the guy and his publicly exposed conduct months after any impeachment process will have ended. (If we can't vote Trump out, do we really deserve to govern ourselves?)
The strongest argument for impeachment, in my view, is that the President is attempting to rig the next election, i.e. that we cannot “let the voters decide,” because if we don’t oust the sonofabitch, the voters won’t actually be able to decide. But our politics features the sage observation “he stole it fair and square.” One test of a political leader is the ability not to be taken advantage of by bad actors. If Trump can steal the election from you, then Putin could probably steal the world from you.
I believe Trump won the nomination because none of his opponents could actually humiliate him, despite his being the worst person ever to run for the office. There they were, up on the stage, being asked if they would back the GOP nominee whoever it turned out to be. Only Trump refused to raise his hand. Any decent candidate would have joined him and said, loud and clear, that if the Party nominates Trump, he or she would do everything in his power to defeat him. Instead, these would-be “leaders” showed a level of cowardice completely incompatible with the presidency. The question might as well have been “Who is too stupid to see that Donald Trump should not be President of the United States?” They answered that question honestly, and the rest is history.
The Democrats and the electorate both need to redeem themselves for their horrid performance in 2016. If either fails to do so, then a strong case can be made that we do not deserve to govern ourselves. Who knows? Maybe that is in fact the case. Maybe democracy has hit the wall of diminishing returns, where everything people can agree to do has been done, and all that's left to do are things we must be forced to do. There is no rule of nature that says otherwise. Seems an important thing to discover, though, and having Trump on the ballot in 2020 strikes me as the best possible way to discover it.