Impeaching Donald Trump would be an act of political symbolism; there is not going to be a supermajority in the Senate to convict him. There is no way of knowing for sure how the politics will play out. (Bouie’s appropriately careful and tentative defense is the best one I’ve seen.) What limited data we have, however, lends no support to the idea that it would be good politics. The public opposes impeachment proceedings — let alone impeachment — by nearly
2-to-1 one-and-a-half-to-one margins. Nor does it seem to be a significant priority for most engaged voters. The only historical example of a president being impeached with no serious threat of removal led to the president’s popularity increasing and the president’s party doing unusually well for an in party in midterm elections. (I’ve seen people argue that impeaching was in fact political genius because of Bush’s victory in 2000. This is really dumb, not least because Bush’s extremely fluky win relied on a bunch of things — including a faulty ballot design by a Democratic official and Ralph Nader’s pure anti-Democratic ratfucking campaign getting much more traction than his 1996 one did — that were beyond their control. And of course there’s another crucial difference, which is that Clinton couldn’t run again.) Obviously, we don’t know if it will play out the same way. But while Trump is less popular than Clinton was, this cuts both ways — the fact that Trump is already unpopular, combined with the fact that his base is unshakable, makes the political upside of impeachment very limited.
Another problem with arguments that assume impeachment would be good politics is that they focus on the impeachment proceedings, and not the Senate trial. The impeachment process doesn’t end with Trump being impeached; it ends with a Republican-led Senate trial that almost certainly fails to even secure a simple majority to convict. And anybody who thinks the dominant media narrative will be “corrupt Republican majority protects Trump” as opposed to “Vindicated Trump Found Innocent, Dems in Disarray After Failure of Partisan Witch Hunt” has not paid any attention to American politics for decades. There will be obsessive focus on Manchin and whatever Dem House backbenchers cast immaterial votes against conviction/impeachment.
There are exceptions, but in my experience most strong advocates of impeachment don’t really accept the reality that impeachment can’t remove Trump. Defenses of impeachment tend to lead to arguments like “you can’t win if you don’t even try,” comparisons to hardball actions that would actually carry substantive benefits (like eliminating the filibuster), etc. People argue that if you don’t impeach Trump that means he’ll get away with it, but if course if he’s impeached and not convicted he also gets away with it, and no material constraint has been placed on the misconduct of future presidents. And of course among less-informed voters it’s an even bigger problem because impeachment and removal tend to be conflated. In most cases, when people say they’ll applaud Democrats for fighting and losing, I don’t believe them. Murc’s Law is a harsh mistress.
David observed recently that a lot of the advocacy for impeachment is a liberal version of Framer/Constitution worship. Trump is so obviously unfit for office it’s hard to accept that there is no effective means of removing him. But there isn’t. Like a lot of the constitutional mechanisms the framers thought would constrain bad actors, the impeachment/removal process just doesn’t work given contemporary partisan norms. Given this reality, I don’t see much value in pursuing an impeachment most voters don’t want. Dem leaders shouldn’t preemptively rule out impeachment, but unless something changes active congressional investigation is the better anti-Trump approach.