Treason?  Impeachment?   High Crimes?   Misdemeanors?   
The offenses, for which presidents, vice-presidents and all civil officers (even, perhaps, Pelosi and Schumer as well?) and federal judges can be removed from office, is a process called IMPEACHMENT. 
The phrase called “HIGH CRIMES AND MISDEMEANORS” is found in the Constitution of the United States of America.  These words have broad meaning in U.S. law.  They can either be serious criminal or civil ALLEGATIONS.  Examples of the latter would be misuse or abuse, such as perjury of oath, abuse of authority, bribery, misuse of assets, dereliction of duty, failure to supervise, intimidation, refusal to obey a lawful order and chronic intoxication.  There were linguistic arguments as to the differences among TREASON, BRIBERY, HIGH CRIMES and MISDEMEANORS.  The latter two are vague, broad-based and not nearly as specific as those involving TREASON or BRIBERY.  
The framers intended for removal from office to be the final step in a two-part process that begins in the House of Representatives.  Should charges result, the second step would begin.  That would be a trial-like hearing before the Senate.  A two-part process accomplishes two goals:  (1) A full public inquiry into the ALLEGATIONS and (2) the ADJUDICATION of those charges, requiring a 2/3 senate majority for removal.    
In 1974, the House Judiciary Committee recommended that the House approve Articles of Impeachment against Nixon.  It didn’t cite a single impeachable offense; instead, it found a broad pattern of wrongdoing.  There was confusion and debate in seeking a clear definition.  Finally, it found that Nixon and his advisers had conspired to obstruct the “Watergate break-in” investigation.  Nixon resigned before the process could continue.
In 1998, the House Judiciary Committee recommended that the House begin IMPEACHMENT proceedings against Bill Clinton.  The House concurred, approving  two of the four articles of impeachment.  The trial moved to the Senate, which failed to garner the necessary 2/3 majority to remove Bill from office.