You can only be ELECTED for POTUS for 2 terms, you can serve longer by filling the presidents unexpired term if less than 2 years and that time will not count against you. Ex. LBJ filled 1yr 29 days of JFK's term, won reelection for 4yrs, then attempted another term but withdrew, had he been reelected he would have served a total 9yrs 29 days as POTUS. Ford served more than 2yrs for Nixon's term so he was only eligible for 1 election for POTUS