But what if he's no longer President. What if he loses in november? He cannot be impeached then. So, is he just off scott free?
Once he is out of office he loses the protection of the Constitution and any prosecutor with jurisdiction can prosecute him.
Since the fraud was perpetrated under the electoral laws of each of the 50 states, as well as being a violation of federal law, any local district attorney and any U.S. attorney in any of the 50 states could seek an indictment (or, depending on local law, file an information) against Obama.