Here is one for you. (Also do note that we have an ongoing investigation).
http://litigation.findlaw.com/legal-system/presidential-impeachment-the-legal-standard-and-procedure.html
basically it is up to the House to make the determination, but this might help
(#3)
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.