For the historical record, Truman never joined the KKK. His affiliation with the Democratic Party, was undoubtedly based upon his family's history. His grandfather was a Confederate Civil War veteran and Truman's early writings showed some use of the "N" word. (As president later, he was successful in pandering to black voters by pushing some civil rights initiatives.)
Suppose you could call Truman a Democratic hack, as his early political career was aided and abetted by the powerful Pendergast machine in Jackson County, Missouri. But thereafter he was usually not thought of as big city machine politician, but more of a common man.
Surely his foreign policy as president would eliminate him from obtaining high office in today's 'Rat Party. One would have to admit that he was a staunch anti-communist, and he did agree - though reluctantly - to require federal employees to sign a loyalty oath.
Truman’s foreign policy blunders, hard left economic platform, incompetence, corruption, and blindness to communists right under his nose in his own government, makes him fit right in with the pantheon of horrible RAT Presidents.