One thing you don't bother to acknowledge...... The House passed on Feb 6, 1974 a resolution passed a resolution by a vote 0f 410 - 4 to give formal authority to its Judiciary Committee to launch an impeachment hearings. On April 11, 1974, May 15, 1974, May 30, 1974, and June 24, 1974, Nixon did not turn over any items as demanded by subpoenas issued by the Judiciary Committee. That is where Article III of the impeachment that Lindsey Graham is talking about comes from. After the House voted to formally consider impeachment Nixon's refusal to comply interfered with their right to go through the impeachment process. As the House stands now the House can request or subpoena items from the executive branch and the executive branch in return can claim executive privilege. Than the courts will sort it out. Come back to complain when there is an official impeachment hearing and Trump is doing what Nixon did which was outright ignoring subpoenas. Oh and continue to be amazed by the Democrats who don't use their subpoena power that they currently have but instead send letters asking for information. Ask yourself why they don't want a court fight.