An Additional Point

TPM Reader DK has a good point. Leaving these to one-off decisions by the Chief Justice as presiding officer has the additional possible advantage of avoiding some damaging precedents …

I have read your discussion of a Senate impeachment trial with John Roberts in the role of presiding officer. The take away being that the Democrats don’t need to wait for a Supreme Court decision to subpoena witnesses (Mulvaney, et.al.) with direct knowledge of White House actions. Instead a witness could be called during a Senate trial, and if Roberts were to overrule objections, they would have to testify.