“It is something that is widespread in black circles,” said Representative Emanuel Cleaver II of Missouri, who like Mr. Cummings is an African-American Democrat who has been approached repeatedly by voters expressing such a concern. “I’ve been hearing this for some time: ‘Well, the Secret Service, they’re trying to expose the president.’ You hear a lot of that from African-Americans in particular.”…

Donald W. Tucker, one of the first black members of the Secret Service, who retired from the agency in 1990 and wrote a book about his experiences, said that he had no reason to believe the agency had not protected Mr. Obama vigorously but that he heard the concern regularly.

“I would say over 75 percent of the African-American community are suspicious and think that could be a situation, based on all the other things they think has happened to President Obama because he’s an African-American, politically,” he said. “They’re adding that to the pot.”