INDIANOLA, Miss. — When Mike Espy, a young black lawyer from a prominent local family, first campaigned for Congress in this tidy Delta town 30 years ago, many white voters refused to shake his hand. The onetime home of both B. B. King and the White Citizens’ Council, Indianola embodied the gulf that has divided Mississippi for centuries.

But last week, when Mr. Espy, the former House member and President Bill Clinton’s agriculture secretary, returned seeking an improbable Senate seat, the town’s white mayor joined him for lunch at a barbecue joint. A black proprietor serenaded him a cappella, as if he were a celebrity of sorts: “Go get that senator’s race,” he boomed.

“There are very few who would not consider me because I am black,” Mr. Espy, 64, said as he strolled through Indianola after lunch. “I believe we in many ways have crossed that hurdle. Many of them, if they don’t vote for me, it will be because of their idea of what I represent as a party person.”

That would be the Democratic Party, and yes, it is a problem. Mr. Espy would be Mississippi’s first black senator since Reconstruction, but the bigger obstacle may be a more modern one: convincing voters in an overwhelmingly Republican state to break partisan ranks and support a party that has gone all but extinct in major offices in this part of the South.