OK about Washington, since he had to set a precedent. Surely we can trust the voters if they want to re-elect an incumbent president who's doing a reasonably good job? Obviously they all won't run four times, most presidents are in mid 50's at the beginning of their term, and they get too old and tired, or exhaust their political capital. In OTL, Ike wouldn't run in '60, Reagan wouldn't be elected at age 77, and Bush would win no state north of Mason Dixon in 2008. As per my TL, it can be proposed, but it doesn't have to pass. For FDR, they knew he would die in office (he proposed to resign at the end of WWII), but the Dems had no choice. Truman was too unknown, Wallace was far too radical, and otherwise Dewey would win. That Obama idea might be a good idea for the Dems here, since it appears that he has no foreseeable successor. The GOP has about 5 or 6 possibilities.