“If Bernie Sanders is atop the ticket, it’s going to make it tougher for all of us to win in Florida,” Fernandez said.

Sanders shot back on Monday, declaring: "Truth is truth. All right? If you want to disagree with me, if somebody wants to say that — and by the way all of the Congress people you mentioned just so happen to be supporting other candidates ... but you know, the truth is the truth. And that is what happened on the first years of the Castro regime."

Sanders added that China is another example of an autocratic dictatorship that has accomplished good things for its people.

"China is an authoritarian country, becoming more and more authoritarian," Sanders said. "But can anyone deny, the facts are clear, that they have taken more people out of extreme poverty than any country in history?"

Sanders' remarks on “60 Minutes“ came as many voters remain concerned about his past refusal to totally condemn Soviet-backed leaders. Sanders had previously argued that Castro had done some good things for his country, including expanding health care and education to the poor.

Still, Sanders emphasized Monday that he is adamantly opposed to authoritarian states and their methods of ruling.

"I think teaching people to read and write is a good thing. I have 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."

Fellow Democratic candidate Pete Buttigieg, who has critiqued Sanders as being polarizing and too far left, expressed dismay at Sanders' comments. He has frequently clashed with Sanders — claiming to be a more moderate candidate set to appeal to independents and Democrats alike — and claimed Sanders would not be able to appeal to voters who had previously supported Trump.

"I don't want as a Democrat to be explaining why our nominee is encouraging people to look on the bright side of the Castro regime when we are going into the election of our lives," Buttigieg said during his CNN town hall Monday night.

He added: "Of course literacy is a good thing, but why are spotlighting the literacy programs of a brutal dictator instead of being unambiguous in our condemnation about the way he has treated his people?"

Democratic candidate Tom Steyer went so far as to say he would never speak highly of unelected leaders who rule without any democratic checks on their power.

"I don't think it's appropriate to be giving him a lot of compliments," Steyer said during his CNN town hall. "I think we're in a different situation. The United States is supposed to be the value-driven leader of the world."