Representative James E. Clyburn of South Carolina, the highest-ranking African-American in Congress, said he was rethinking his neutral stance in his state’s presidential primary out of disappointment at comments by Bill and Hillary Rodham Clinton that he saw as diminishing the historic role of civil rights activists.

“To call that dream a fairy tale, which Bill Clinton seemed to be doing, could very well be insulting to some of us,” said Mr. Clyburn, who said he and others took significant risks more than 40 years ago to produce such opportunities for future black Americans.”

Civil Rights Tone Prompts Talk of an Endorsement