? He was republican (allegedly).. and white democrats in the south became republicans...? Idk where you are going with that or like.. why you're bringing dem vs repub into it now ? Or what your source is on his political party for that matter...
According to Encyclopedia Britannica, he wasn't officially repub or dem.
He was not formally affiliated with either political party. Nor did he explicitly endorse any candidate. In fact, he stated, “I don’t think the Republican Party is a party full of the almighty God, nor is the Democratic Party. They both have weaknesses. I’m not inextricably bound to either party.”
King biographer David J. Garrow claims King was fond of some Republican politicians, such as Richard Nixon, although it is almost certain that he voted for Democrats JFK in 1960 and Lyndon Johnson in 1964. (According to Time.com, JFK had called a governor to try and get him out of jail once when he got sentenced to 6 months hard labor over a protest... Nixon did nothing. And this led to MLK to kind of flip on Nixon.... " this is why I really considered him [Nixon] a moral coward and one who was really unwilling to take a courageous step and take a risk. And I am convinced that he lost the election because of that. ")
He also denounced Republican presidential candidate Barry Goldwater, who, as a senator, had voted against the Civil Rights Act of 1964. King said in an interview, “I had no alternative but to urge every Negro and white person of goodwill to vote against Mr. Goldwater and to withdraw support from any Republican candidate that did not publicly disassociate himself from Senator Goldwater and his philosophy.” Although King supported Johnson’s presidential campaign, he later spoke out about his dissatisfaction with Johnson’s handling of the Vietnam War.