STO,  
Exactly what proven  'sexual assault'  are you referring to? 

   Bill Clinton used the office of President, in more than one way, to seduce a very young intern.  It wasn't 100% consensual using a title  lX   view of most employer related work place sex harassment rules as this was a boss having an employee perform a lewd act on him. He wasn't impeached for the sex though, it was for lying about it to a Grand Jury. He perjured himself and was impeached in the House of Representatives.