The GOP position is that, if President Trump thinks he did nothing wrong, he can deny the validity of an impeachment proceeding and refuse to participate at all, because if he ever did commit an impeachable offense he'd recognize the proceeding was valid and cooperate in full.
The GOP position is it's fine for the President to deny the existence of Congress's powers, because Congress can always take it to the courts and get the issue partially resolved in 8-16 months, and there's nothing a President can do in that time span that would be too concerning
The GOP position is that when a Chief of Staff goes on live TV and says that military aid to an ally was withheld due to the President's desire for an investigation, then it is a baseless partisan fishing expedition for Congress to investigate whether that did in fact happen.
The GOP position is that it's fine for Trump to ask Zelensky to investigate the Bidens, because Zelensky has said he didn't feel any pressure, and requesting a foreign state to interfere in a U.S. election is fine so long as that foreign state is a genuinely willing participant.
