Herman Cain, a business executive who sought the Republican nomination in 2012, had been hospitalized with the coronavirus in the Atlanta area. He attended Mr. Trump’s rally in Tulsa, Oklahoma in June 2020 and tested positive for the coronavirus shortly after. Mr. Cain rose from poverty in the segregated South to become chief executive of a successful pizza chain and then thrust himself into the national spotlight by seeking the 2012 Republican presidential nomination. Mr. Cain was 74.