I gather from your comment that you do not like some aspects of the system of government we were given. In this sense, I consider you an ally. I am also glad to see that you and I agree that the president is not above the law. The Constitution specifies that a president may be impeached for "treason, bribery and other high crimes and misdemeanors". Evidence for such offenses can come from a variety of sources inside and outside the executive branch.
President Nixon was not impeached for firing Cox. The House Judiciary Committee passed three articles of impeachment. The full text of those articles is available
here. I presume that firing Cox was not listed because that firing was a constitutionally protected act. Nevertheless, that firing (and the associated Saturday Night Massacre) led to massive public outcry and therefore to a serious threat of impeachment on other grounds. Similarly, President Trump would be well within his authority to fire Robert Mueller. However, I believe that the political fallout from such a firing would be too great for the president to withstand.
So is your position that President’s action CAN constitute obstruction if done to interfere with an investigation into his wrongdoing? Because that is part of what Nixon was impeached for.
From Nixon’s impeachment articles:
“Richard M. Nixon, using the powers of his high office,
engaged personally and through his close subordinates and agents, in a course of conduct or plan designed to delay, impede, and obstruct the investigation of such illegal entry; to cover up, conceal and protect those responsible; and
to conceal the existence and scope of other unlawful covert activities.” (particular emphasis on conceal the existence and scope.. very appropriate to Trump’s apparent plan)
*approving, condoning, acquiescing in, and counselling witnesses with respect to the giving of false or misleading statements to lawfully authorized investigative officers and employees of the United States and false or misleading testimony in duly instituted judicial and congressional proceedings; (Don Jr’s false statement on the Magnitsky Act meeting, anyone?)
** interfering or endeavouring to interfere with the conduct of investigations by the Department of Justice of the United States, the Federal Bureau of Investigation, the office of Watergate Special Prosecution Force, and Congressional Committees; (obvious)
***approving, condoning, and acquiescing in, the surreptitious payment of substantial sums of money for the purpose of obtaining the silence or influencing the testimony of witnesses, potential witnesses or individuals who participated in such unlawful entry and other illegal activities; (Paying off fired administration officials through 150K/year consulting gigs with the RNC)
**** making or causing to be made false or misleading public statements for the purpose of deceiving the people of the United States into believing that a thorough and complete investigation had been conducted with respect to allegations of misconduct on the part of personnel of the executive branch of the United States and personnel of the Committee for the Re-election of the President, and that there was no involvement of such personnel in such misconduct: or (Witch Hunt! 13 Angry Democrats!)
*****endeavouring to cause prospective defendants, and individuals duly tried and convicted, to expect favoured treatment and consideration in return for their silence or false testimony, or rewarding individuals for their silence or false testimony. (Manafort pardon offer)
I should have reviewed this material a while ago! The parallels are striking.
Furthermore, the fact that Nixon was impeached for interfering with the investigation not just by Congressional Committees, but by various arms of the DoJ, shows that your President-as-unbridled-executive theory is not shared by Congress. He does not have absolute authority over the executive branch, at least in the case of using his authority to obstruct investigations.