WASHINGTON — Supreme Court nominee Clarence Thomas is a young man not yet set in his views, not opposed to affirmative action, and the only chance President Bush will give the United States Senate of confirming a black justice to the court.This is the picture drawn at a Monitor breakfast this week by Judge Thomas's mentor and Senate champion, Sen. John Danforth (R) of Missouri. One administration official has told him, said Senator Danforth, that no other blacks are on the White House list of potential Supreme Court nominees. If Thomas is not confirmed, Danforth said, "I think there is no chance, as a practical matter, that there would be a follow-on black." The Congressional Black Caucus opposes Thomas because of his civil rights views. The Urban League has decided not to take sides; its members are too divided. Some accuse Thomas of opposing affirmative action programs which made his achievements possible. But Danforth said: "He does not believe in numerical quotas, but he does believe in outreach and he does acknowledge that he has been helped along in his life by the civil rights movement." Thomas created an affirmative action program for the Equal Employment Opportunity Commission as its chairman, Danforth noted, as well as establishing a college scholarship fund for disadvantaged students. "I think it's important for at least some of the members of the Supreme Court not to be totally pre-formed before they arrive on the court," Danforth said. The senator acknowledges that the kind of organized campaign that defeated the Robert Bork nomination in 1987 is still possible: "Obviously, in the post-Bork era, there is concern that during the month of August opposition can be ginned up."