Have any of the US Presidents ever, upon completing his first term, simply not run for a second?
TIA!
–FCOD
LBJ opted not to run in 1968.
John Tyler sort of didn’t. He was thrown out of his party for vetoing the charter for the Bank of the United States. With no party to run for, and virtually no support he withdrew his candidacy in August. Whether that means he voluntarily didn’t run I’ll leave to the OP to decide.
A similar thing happened to Buchanan.
James K. Polk:
Truman could’ve run in '52 after having served one term plus the partial term he inherited from FDR, but chose not to.
Calvin Coolidge didn’t run in 1928. Not technically his second term, but it would have been his second elected term.
And, Theodore Roosevelt opted not to run for a second elected term in 1908 since his first term after succeeding McKinley was close to a full term.
But he ran again in 1912.
The most anyone can serve as President is 10 years (VP to President with less than two years left in the former President’s term plus 2 full terms of his own.) FDR died in 1945, meaning that Truman basically served two full terms from 1945-1953. The 22nd amendment was ratified in 1951. However, you are right that Truman was excluded from the 22nd amendment and could have run if he wanted to (or had done better in the primaries.)
Thanks, everyone!
–FCOD
Going way back to the early- to mid-1800s, there were quite a few Presidents who did not run for a second term: Tyler, Polk, Pierce, and Buchanan all served only a single term (or less, in the case of Tyler,who took over for W.H. Harrison), and did not run for a second term. Fillmore replaced Taylor (who died in office in 1850), and ran again against Buchanan in 1856 (Fillmore skipped the 1852 election). Johnson, Hayes, and Arthur did not run for re-election, either. Good, brief summaries of the Presidents are available at the Internet Public Library Presidents site. With it being Independence Day today, all the US Dopers should read them all! 
It seems that during earlier times it was considered poor form to presume you should be re-elected, and also poor form to actively campaign on your own behalf, even for your first term.
It’s difficult to give an unambiguous list of presidents who didn’t seek re-election, because of the different manner in which party nominations were determined in the Nineteenth Century. There were no primaries, and little occasion to “announce one’s candidacy” for a party nomination; indeed, open campaigning would have been considered gauche. Rather, one’s supporters would work behind the scenes to try to elect delegates at state conventions and sway delegates after they had been elected.
Fillmore, Pierce, A. Johnson, and Arthur all failed to win their party’s nomination for either a full term or a second term, but in every case there were active movements on their behalf at the party convention, which they did not discourage. So in every case, by the standard of the time, one would have to say that they sought re-election. Tyler simply had no support in either party, so no movement on his behalf developed.
There were three presidents, however, who stated their intention to serve only a single term upon taking office, never wavered, and never allowed any movement on their behalf for renomination. The three were Polk, Buchanan, and Hayes. So the answer to the OP is an unambiguous “yes”.
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