THIS COULD GET DICEY & very UGLY... "...The Senate has options for scuttling the impeachment process beyond a simple refusal to heed the House vote. The Constitution does not specify what constitutes a “trial,” and in a 1993 case involving a judicial impeachment, the Supreme Court affirmed that the Senate’s “sole power” to “try” means that it is not subject to any limitations on how it could conduct a proceeding. Senate leadership could engineer an early motion to dismiss and effectively moot the current rule’s call for the president or counsel to appear before the Senate. The rules in place provide at any rate only that “the Senate shall have power to compel the attendance of witnesses”: they do not require that any other than the president be called. Moreover, the Senate could adjourn at any time, terminating the proceedings and declining to take up the House articles. This is what happened in the trial of Andrew Johnson, in which the Senate voted on three articles and then adjourned without holding votes on the remaining eight."

SOURCE: https://www.lawfaremedia.org/article/can-senate-decline-try-impeachment-case