Actually, I believe the intent of impeachment is not to punish the President for past wrongdoing based on the standards of criminal law — it is, rather, a prospective judgment made to prevent the President from engaging in reasonably foreseeable indiscretions and/or violations that would bring the Presidency into disrepute. It is a political process as much as a legal one, which favours Trump to an extent, however, even Republicans may be unable to defend Trump if it is demonstrated that Trump is cashing in on his office contrary to the "emoluments clause" in the Constitution.