What was the motive of voters and politicians who supported segregation?

[smoltchanov]

Power. The guaranteed way to hold power without neccessity to share it with large Black population of Southern states was segregation and denial of voting (and other) rights to Blacks. And, in addition, that was a very good way "to attach" poor whites to the rich one (despite absolutely different economic interests), and to prevent a possibility of creation of "dreadful" populist coalition of Blacks and poor whites. 2 goals achieved simultaneously.....