Conventionally, the House’s impeachment has been likened to an indictment in a criminal case—and of course, evidence not used to support an indictment can still be introduced at trial. McConnell’s claim, a conservative refrain, shows that he is operationalizing a different metaphor. As Benjamin Wittes observed recently at Lawfare, this line of argument imagines the House as a trial court and the Senate as a court of appeals. Any arguments and supporting evidence that the House fails to pursue at trial it forfeits on appeal to the Senate.
The Senate’s willingness to make good on this (re)vision of the responsibilities of and relationship between the chambers changes the game for the House going forward. That’s the thing about the impeachment playbook: It’s short, so each entry gets enormous playback. The Constitution itself says very little about how the House and Senate must conduct their proceedings, so the norms and rules set by the chambers themselves in a given impeachment are dissected for decades and become the baseline from which future impeachments are judged and future plays strategized. For this reason, even the extreme partisan rancor that suffused these proceedings probably could not have fully prepared the House, or the country, for the Senate’s decision to see no evidence and hear no witnesses.
Now everyone knows the play for a House impeachment followed by a trial in a defiant Senate. The expectation that the Senate will claim the limitations of an appellate body and not only acquit but also decline to investigate a president of its own party generates a new set of defaults for future impeachments of constitutional conscience.