The challenge is to make the New Negro movement, which started in the late 1910s by WWI veterans, more successful, such as break down racial segregation and implement integrationist policies. Kudos if it causes a reactionary to be elected in the early 1920s and causes even more racist policies to be implemented.
Well, TBH, I'm afraid the latter would be extraordinarily tough to pull off(yes, even if the KKK did peak at 3-4 million in the 1920s, that's still only 3% of the total American population, and maybe something on the order of, say, 15% of all the right-wingers.), without some sort of 3- or 4-party tie a la 1824, and/or the movement in question being full of, say, radical American-style Bolsheviks.....probably both; Woodrow Wilson was the closest we could have gotten, and he was only semi-reactionary in a social/civic sense at his worst(especially for his time period).
But with the former, while sadly probably damn near impossible in the South(except maybe for areas of Texas, Florida, and a few other places, maybe Louisiana if Huey Long still comes to power), this can be done without much difficulty in much of the North; an appeal to the Constitution would no doubt grab many ears, and open at least some minds up to eventually bringing around full integration. There is, however, still the issue of racially-tinged corruption, not just in government(such as with the police), but in other areas, too, such as real estate(where some of the worst problems happened IOTL, such as intentionally gouging housing values whenever minorities moved in to a mostly "white" neighborhood), etc.