WHY didn't all demo Democrats support harry Truman in 1948?

Not all Democrats supported Harry Truman in 1948 due to ideological divisions within the party. Some Democrats, particularly Southern delegates, opposed Truman's civil rights initiatives, which sought to address racial segregation and discrimination. Additionally, the emergence of the Progressive Party, led by figures like Henry Wallace, attracted more liberal and left-leaning Democrats who felt Truman was not progressive enough. These factions contributed to a fractured party, leading to differing levels of support for Truman's candidacy.