His announcement on Monday came nominally in response to a question about whether his plan for free college was equivalent to President Trump’s promise to build a border wall and make Mexico pay for it: a rallying cry for supporters, but with no realistic path to happening.

But he had clearly anticipated an opportunity for the reveal, because he had a piece of paper ready to pull out of his pocket.

“I thought that question might come up. All right. Here it is,” he said. “This is a list, which will be on our website tonight, of how we pay for every program that we have developed.”

Within minutes, there it was.

Later in the forum, the most inevitable subject of the night came up: Mr. Sanders’s declaration on “60 Minutes” on Sunday that, while he opposed the authoritarianism of Cuba’s government, “it’s unfair to simply say everything is bad.”

“When Fidel Castro came to office, you know what he did? He had a massive literacy program,” he said in that interview. “Is that a bad thing? Even though Fidel Castro did it?”

Those comments angered many Cuban-Americans, who are a powerful voting bloc in Florida. Asked about his comments in the town hall on Monday, Mr. Sanders repeated the example of Castro’s literacy program and said he had been “extremely consistent and critical of all authoritarian regimes all over the world, including Cuba, including Nicaragua, including Saudi Arabia, including China, including Russia.”

“I happen to believe in democracy, not authoritarianism,” he said. But, he added: “China is an authoritarian country, becoming more and more authoritarian. But can anyone deny — I mean, the facts are clear — that they have taken more people out of extreme poverty than any country in history? Do I get criticized because I say that? That’s the truth.”