At least five veterans of [the march on Washington] traveled to Denver this week as Democratic delegates, among them Representative John Lewis of Georgia, who is the last man alive of the 10 who spoke that day at the Lincoln Memorial. This son of sharecroppers, who was almost beaten to death by police officers in Selma, Ala., when he marched with civil rights activists across a bridge, stood on a sun-splashed street in Denver and considered the distance traveled.

His bald head still bears near half-century-old scars.

"We've had disappointments since then, but if someone told me I would be here," Mr. Lewis said, shaking that head. "When people say nothing has changed, I feel like saying, 'Come walk in my shoes.' "