https://www.americanthinker.com/blog/2020/01/mitch_mcconnell_promises_a_meritorious_wellrun_impeachment.html
In a court of law, a party on the receiving end of civil or criminal charges can move to dismiss those charges if he can prove that the charges do not state a case for which relief can be granted. This argument can be made either on the ground that the law does not recognize the claimed cause of action or criminal charge, or that the facts stated in the opening papers fail to meet the requirements for such a cause of action or criminal charge. The president’s opening papers show that his attorneys will argue that the Articles of Impeachment fail under both of these metrics.
For some time, however, Republicans have been concerned that the Senate will not allow the equivalent of a motion to dismiss. Instead, they’ve fretted that the Senate will give credibility to the fatally flawed Articles of Impeachment by allowing a full evidentiary trial. Even assuming Trump were to prevail in the impeachment proceedings, his opponents would still argue that the claims were valid enough to merit a full hearing.