The Constitution doesn’t tell us very much about how the impeachment process is supposed to work. Our legal system gives us two plausible models for it:
1. GRAND JURY/TRIAL: The House serves as a sort of grand jury and creates the indictment; the Senate handles the trial. Following this model, the president has few rights in the House, and live witnesses are necessary in the Senate.
2. TRIAL COURT/APPELLATE COURT: The House actually holds a trial with live witnesses, participation by the president’s counsel, and cross-examination. After the House creates a complete record, the Senate reviews it and makes its own legal conclusions. No witnesses are necessary in the Senate process.
The problem with the current process is that it is neither of the above. The reason for that, in a nutshell, is that the House leadership did not, and could not, know how the Senate trial would be run. As a result, what we are likely to have is a mixed process: grand jury/appellate court. Politically, that may fly, but legally and logically, it makes no sense whatsoever.
In today’s world, I guess that figures.