Likelihood that this will be the map

[ag]

To the best of my knowledge, Truman never really planned to run for nomination in 1952. It was his firm view that 2 terms was enough - and he had almost complete 2 terms in office. He did held off announcing it long past the decision - obviously, it helps not being perceived as a lame duck. But he never planned to run. Had he tried, I'd hate to discard him - he had won in 1948 against, probably, worse odds, hadn't he?

[ag]

In 1948 there was a three-way split of the Dem party. Would there still be one in 1952 were Truman to be nominated? Also, arguably, he'd think more of his own popularity had he been planning to run for office again - those numbers you see in early 1952 (which are not that far below his abysmal numbers in 1948) are, at least in part, endogenous to his decision not to run.