Sen. Amy Klobuchar of Minnesota made an important point early in the Democratic presidential debate when she acknowledged that one could believe certain conduct is “impeachable,” but still at least try to maintain formal objectivity until all the evidence and arguments have been presented.

Klobuchar gave everyone a bit of a civics lesson by saying there are good, formal reasons for senators to withhold final judgment on whether President Trump should be removed from office until the Senate actually holds a trial. She spoke, not quite literally but by very close analogy, about senators’ “job as jurors” that involves actually listening to the evidence. Even if senators are largely convinced that Trump’s conduct merits removal, they should strive to keep an open mind — and, at least as importantly, they should maintain a public show of at least attempting impartiality.