Herman Cain, Former C.E.O. and Presidential Candidate, Dies at 74

“We knew when he was first hospitalized with Covid-19 that this was going to be a rough fight,” Mr. Calabrese said in the announcement, adding, “Although he was basically pretty healthy in recent years, he was still in a high-risk group because of his history with cancer.” Mr. Cain had overcome colon and liver cancer in the mid-2000s.

Mr. Cain had attended President Trump’s indoor rally in Tulsa, Okla., on June 20 and had done “a lot of traveling” recently, Mr. Calabrese said.

“I don’t think there’s any way to trace this to the one specific contact that caused him to be infected,” he said at the time. “We’ll never know.”

In a video posted to his website after the Tulsa rally, Mr. Cain said he had worn a mask while he was in groups of people. But he also posted photographs of himself on social media that showed him without a mask and surrounded by people in the arena. Later, after Mr. Trump had scheduled an event at Mount Rushmore in South Dakota, Mr. Cain wrote approvingly on Twitter that masks would not be mandatory. “PEOPLE ARE FED UP!” he wrote.