There is no such thing as a president throwing out an election and calling a new one. The Constitution gives the choice of electors to state legislatures, who over the years have passed that duty on to the electorate. You could have the legislatures end presidential elections in their states or simply override the choice of the voters. Both would be politically unpopular, but still legal.
Obama getting a third term would be such an open violation of the Constitution that it would not stand. Even Obama knows that.