Good question.
Charles Blow answers your question quite simply just today:
Racism is simply the belief that race is an inherent and determining factor in a person’s or a people’s character and capabilities, rendering some inferior and others superior. These beliefs are racial prejudices.
The history of America is one in which white people used racism and white supremacy to develop a racial caste system that advantaged them and disadvantaged others.
So the ulterior motive of the racism is power, but here's the key clue how it works in modern politics:
Racism doesn’t require hatred, constant expression, or even conscious awareness.
The racism is already built into our system and the racist politics of today are manifested in conservatism striving to maintain that systemic racism, that is, making sure those in power stay there. I, a white male, without any doubt have taken advantage of it throughout my life. The difference between me and the racist (by the above definition) conservatives here is that I advocate ending that power differential and creating a fair game for all.