The former mayor saw his biggest, most enthusiastic crowds in Bentonville, the headquarters of Walmart, where a mostly white crowd of over 1,000 people came out to see him on a chilly night.

Mr. Bloomberg was introduced by John Burkhalter, a well-known entrepreneur and the state’s former highway commissioner. In a rousing speech, Mr. Burkhalter, clearly more charismatic than the headliner, noted that Mr. Bloomberg was self-made. “Michael Bloomberg has lived the American dream, and he wants you to live the American dream!” he shouted, eliciting raucous applause and shouts of “That’s right!”

In recent days, though, the mood of the Bloomberg campaign, once jubilant, has dimmed after a one-two punch.

First, the former mayor’s disastrous performance in the Feb. 19 debate.

Second, and far more important, was Joe Biden’s decisive victory in South Carolina on Saturday, giving Mr. Biden momentum that could close off Mr. Bloomberg’s pathway to the nomination.

Yet interest in Mr. Bloomberg across the Super Tuesday states, where he will appear on primary ballots for the first time, is strong. At Bloomberg campaign events across the South, many described themselves as former Biden supporters nervous that Mr. Biden isn’t up to the job. In Memphis, my Uber driver, a black woman, said she liked Mr. Biden. “But really that’s only because of Obama, you know,” she said with a smile. She voted early for Mr. Bloomberg.

As Mr. Bloomberg campaigned in Selma and across the South, the crowds were largely friendly and upbeat. But at several events, black voters quietly approached me with questions about “the frisk,” as many here call it.

“So when he says it brought crime down, is that right?” Valerie Fitzgerald, 64, asked me at a Bloomberg event in Memphis.