The 22nd Amendment to the U.S. Constitution was passed after FDR broke with the two-term precedent set by George Washington, and was elected a total of four times. It stipulates that the same individual may only be elected president twice. Truman, who was in office at the time of the amendment's passage, could theoretically have run for another term, as the amendment was written to not apply to him, but he chose not to, and probably would have lost had he run again.
So, which subsequent presidents would have run for a third (or more) term?
- Ike is doubtful, as while he was seen as a popular and successful president, the economy was in recession in 1960, and he would have been 70 at the start of his new term, so age would have been an issue
- Kennedy, LBJ, Nixon, Ford, Carter, and Bush Sr did not serve two full terms: Kennedy was assassinated, Nixon resigned, Carter, Ford, and Bush were defeated for reelection, and LBJ opted not to run again, though he could have even with the 22nd amendment in effect
-Reagan is more likely, though he was clearly in failing health by 1988 and his age and health would have been an issue, and I'm not sure he would have been able to meet the physical demands of a presidential campaign. Still, had he run, he probably have won a victory comparable to Bush's
- Clinton very likely would have run for reelection, and probably would have won, though by a considerably smaller margin than either of his first two victories. Despite his personal scandals, he had very high approval ratings at the end of his term
- George W. Bush: who knows. He might have tried, and I'm pretty sure he would have won the Republican nomination, but he would have been defeated in a 46-state blowout