A lot of public opinion researchers want to measure/control for the amount of racism/bigotry in the responses they get and ho it correlates with how respondents answer other questions. But you can't just ask people "are you racist?" because they will obviously say no.
You have to ask them about, say, how they feel about the fact of racial inequality in America — "Do you think this the result of ongoing/historical discrimination or do you think Black ppl need to work harder and make fewer excuses?"
In polls, Republicans unsurprisingly evince a high degree of “racial conservatism.”