The CSM seems to think its legal. You can only be elected president twice per the constitution, but if the president, ie Hillary were to die in office ole Bill could take over until the next election.
http://www.csmonitor.com/USA/Politi...for-Veep-has-crossed-her-mind.-Legal?cmpid=FB
http://www.csmonitor.com/USA/Politi...for-Veep-has-crossed-her-mind.-Legal?cmpid=FB