But what makes Mr. Paul’s approach unique is the broad array of sentencing and voting rights law changes he embraces, positions that often put him at odds with many in his own party.

Why so few other prominent Republicans are aggressively reaching out to blacks is perplexing to some in the party.

“I’m very disappointed that Rand Paul is having to be the bell cow for the Republican National Committee,” said J. C. Watts, the former Oklahoma representative who was one of just a handful of black Republicans to serve in Congress in modern times. “They talk about outreach, but I see very little that they’re doing.”

Referring to Mr. Paul’s approach, Mr. Watts added, “These are things that we should have been doing for the last 25 years.”