Going with the “A President’s power is absolute and accountable to no one” defense.
TV ego Dershowitz is already pitching that “abuse of power” is not a lawful charging theory.
GOP will piggyback and argue that any witness is academic, making the trial a Motion for Summary Judgment.
Link: https://int.nyt.com/data/documenthelper/6703-trump-impeachment/72b283f01b38e37d7f5e/optimized/full.pdf?smid=nytcore-ios-share#page=1