Hi albion,
Under the Constitution, the grounds for impeachment can fall under four different categories. They are: bribery, treason, high crimes or misdemeanors. The Constitution was written in the late 1700's, and so we must look for understanding of those terms as they would have been understood in the late 1700's. There have been people who have investigated the term 'high crimes and misdemeanors' and have found that it was a phrase that had fairly popular use in English law. Using the understanding that the framers of the Constitution would likely have had for the term in the late 1700's, we find that there were quite a lot of possible reasons for which one might be accused of having participated in these 'high crimes and misdemeanors' than outright breaking of a written law.
The general rule that drew a thread pretty much through all of its uses in that day, was some activity or purpose of an elected official that was not in keeping with what was best for the people or the country. Here is how it has been defined previously: "High," in the legal and common parlance of the 17th and 18th centuries of "high crimes," is activity by or against those who have special duties acquired by taking an oath of office that are not shared with common persons. A high crime is one that can be done only by someone in a unique position of authority, which is political in character, who does things to circumvent justice.
Here is a site that discusses how the phrase actually came to be written into our Constitution and how it was defined and understood, in that day.
High Crimes and Misdemeanors - Constitutional Rights Foundation
However, as the investigation works its way through the impeachment process, the process itself may also, just as it did with Clinton, draw out other crimes. For example: One of the charges of impeachment against President Clinton was that he had lied to investigators. That charge couldn't have come about without the investigation having been started. Similarly, we now have President Trump making a fairly strong effort to induce, coerce or threaten people who have been called to testify, to not testify. That activity, brought about by the investigation itself, now makes the argument that the president may be obstructing justice, which is a crime. We have already found that Sonderlin has lied under oath. If the idea of his not being truthful with what he said under oath can be tied to any communication that he had with the administration, then again, the president could be charged with suborning perjury.
What seems to be coming to the front now is that Giuliani is putting himself in the position to be blamed for a lot of the 'request for investigation'. However, if, much like we found in the Michael Cohen testimony, it is found that the president encouraged or directed him to make these requests on the president's behalf, then the president becomes guilty of extortion.
So, a lot of this is going to depend on 'how' the people who are given the responsibility to make the decision of guilt or innocence are going to define these actions and where the dollar stopped, or more precisely, where the effort to do these things started. Did Rudy Giuliani just wake up one morning and think to himself, "I think I'll see if I can get Zelensky to open up an investigation into the Bidens.' Or, did this all start with the president, in private conversation, tell Mr. Giuliani, "Look, you should try to see if you can get Zelensky to open up an investigation into the Bidens."
God bless,
In Christ, ted