I can think of one, but a) it's complex (inadvisable in a televised proceeding relating to an already complex fact-pattern), b) it's confusing (several of its 15 steps could be met with valid objections) and c) I see no need to offer it (Trump has hundreds of GOPers on the case).
PS/ The important thing is that while a defense lawyer could offer a coherent defense, it's not one the client would accept—which is immaterial in a criminal trial, where trial strategy broadly writ is the attorney's prerogative, but matters in a noncriminal political proceeding.
PS2/ Without going into more detail, Trump's best defense is to focus on the 2016 element of his ask of the Ukrainians, present the Biden issue as merely illustrative of a—pre-Biden candidacy—broader concern, and opine that Russian interference was investigated but not Ukrainian.
PS3/ But the legal and factual problems with that defense are *several*, and many of them relate to statements made publicly by the client here (Trump) well *before* the Ukraine investigation started. Those are baseline facts that can't be easily addressed by any defense counsel.
