Democrats can simply make the following points:
1. No real U.S. Senate impeachment trial can be held until the Senate receives an indictment in the form of the Articles of Impeachment delivered from the U.S. House of Representatives.
2. If a meaningful impeachment trial could be held without the Senate actually receiving any Articles of Impeachment, then the Senate could hold an impeachment trial whenever it wanted, regardless of whether or not the House had issued any Articles of impeachment. This is clearly not how the Constitution was written.
3. Therefore, any “trial” that the Senate attempted to hold without having received any Articles of Impeachment from the United States House of Representatives would merely be a sham trial without any legal weight, and any conviction from such a trial would have no legal meaning.
4. Therefore, if Mitch McConnell intends to have a show trial, which has no legal weight whatsoever, and no real meaning whatsoever, we, the Democratic Leaders of the U.S. Senate, feel that there is no legal obligation, and in fact no meaningful purpose, for any Senate Democrat to attend such a show trial. Therefore, no Senate Democrat should feel the need to attend such a farcical event. Pretending that such a show trial would have any legal weight whatsoever would do a disservice to the U.S. Senate, to the U.S. House of Representatives, and to the citizens of America.