Impeachment can be done for any reason whatsoever.
Most reject that interpretation.
https://litigation.findlaw.com/lega...achment-the-legal-standard-and-procedure.html
Presidential Impeachment: The Legal Standard and Procedure
The involuntary removal of a sitting President of the United States has never occurred in our history. The only legal way such can be accomplished is by the
impeachment process. This article discusses the legal standard to be properly applied by members of the U.S. House of Representatives when voting for or against Articles of Impeachment, and members of the U.S. Senate when voting whether to convict and remove from office a President of the U.S., as well as the procedure to be followed.
Article I § 2
of the United States Constitution gives the House of Representatives the sole power to impeach (make formal charges against) and Article I § 3 gives the Senate the sole power to try impeachments. Article II § 4
of the Constitution provides as follows:
"The President, Vice President and all civil officers of the United States, shall be removed from office on impeachment for, and conviction of, treason, bribery, or other high crimes and misdemeanors."
Thus, the operative legal standard to apply to an impeachment of a sitting President is "treason, bribery, or other high crimes and misdemeanors." There is substantial difference of opinion over the interpretation of these words.
There are essentially four schools of thought concerning the meaning of these words, although there are innumerable subsets within those four categories.
Congressional Interpretation
The first general school of thought is that the standard enunciated by the
Constitution is subject entirely to whatever interpretation Congress collectively wishes to make:
"What, then, is an impeachable offense? The only honest answer is that an impeachable offense is whatever a majority of the House of Representatives considers it to be at a given moment in history; conviction results from whatever offense or offenses two-thirds of the other body considers to be sufficiently serious to require removal of the accused from office..." Congressman Gerald Ford, 116 Cong. Rec. H.3113-3114 (April 15, 1970).
This view has been rejected by most legal scholars because it would have the effect of having the President serve at the pleasure of Congress. However there are some, particularly in Congress, who hold this opinion.
An Indictable Crime
The second view is that the Constitutional standard makes it necessary for a President to have committed an
indictable crime in order to be subject to impeachment and removal from office. This view was adopted by many Republicans during the impeachment investigation of President Richard M. Nixon. The proponents of this view point to the tone of the language of Article II § 4 itself, which seems to be speaking in criminal law terms.
There are other places in the Constitution which seem to support this interpretation, as well. For example,
Article III § 2 (3) provides that "the trial of all crimes, except in cases of impeachment, shall be by jury." Clearly the implication of this sentence from the Constitution is that impeachment is being treated as a criminal offense, ergo, impeachment requires a criminal offense to have been committed.
Article II § 2 (1) authorizes the President to grant pardons "for offenses against the United States, except in cases of impeachment." This sentence implies that the Framers must have thought impeachment, and the acts which would support impeachment, to be criminal in nature.
Misdemeanor
The third approach is that an indictable crime is not required to impeach and remove a President. The proponents of this view focus on the word "
misdemeanor" which did not have a specific criminal connotation to it at the time the Constitution was ratified. This interpretation is somewhat belied by details of the debate the Framers had in arriving at the specific language to be used for the impeachment standard.
Initially the standard was to be "malpractice or neglect of duty." This was removed and replaced with "
treason,
bribery, or corruption." The word "corruption" was then eliminated. On the floor during debate the suggestion was made to add the term "maladministration." This was rejected as being too vague and the phrase "high crimes and misdemeanors" was adopted in its place. There are many legal scholars who believe this lesser standard is the correct one, however.
Investigations follow to aid the Senate trial.
The same Senate who just spent two years investigating the matter and found no evidence of collusion or obstruction? For the second time how would the outcome magically change during the impeachment investigation when that same Senate that just closed a two year investigation into the matter is the jury?
Are you suggestion the Senate investigation and Mueller haven't done their due diligence and that there is secret evidence out there that a third investigation is sure to find?
Like I said you're going about it backwards. First evidence of a crime then an investigation into that crime. Not I think this person might have done something but I have no evidence so i'm going to investigate him looking for a crime and until I find one he committed.