He would have to be impeached by the congress and unless control changes with this election, there is very little chance that an impeachment could happen.
"High crimes and misdemeanors" or something like that is the standard. Actually someone, a high placed leagal figure, did go so far as to draw up the papers--I wish I could remember who, and they looked pretty good to me--but as I said, it has to do with the party that controls the congress. Clinton was impeached by a Republican congress and over absolutely nothing--he lied in response to questions he shouldn't have been asked.
AS the little button sayd, "Clinton lied, nobody died. Bush lied, thousands died."