By taking the unusual step of dismissing the head of the US Commission on Civil Rights, President Reagan challenges himself to show whether he means this to be a step forward or backward on civil rights.
The displaced man, Arthur S. Flemming, leaves with warnings about the Reagan administration's ''lip service'' toward equal opportunity. The new man, Clarence Pendleton, arrives with a reputation for opposing the tools of affirmative action and busing to achieve equal opportunity in jobs and schools.
The question is whether Mr. Reagan, who also opposes these tools, will find other means to ensure that America's progress in civil rights is not set back - and whether Mr. Pendleton will fortify the commission's independent and bipartisan role in monitoring and promoting this progress.
After his appointment Mr. Pendleton spoke as if he could accept court-ordered busing for desegregation and affirmative action for those who ''need'' it. But by and large the switch at the commission appears to fit with a number of administration signals reducing federal vigor in support of civil rights. The President must not allow that impression to stand unless he wants the charge of ''lip service'' to stick.