CHARLESTON, South Carolina — Establishment Democrats are in a near-panic over the growing possibility of a Bernie Sanders nomination to be president, fearful that the current front-runner will destroy the party and leave Democrats virtually powerless after November's elections.

Sanders' recent comments about former Cuban dictator Fidel Castro, his refusal to attend an event by a powerful pro-Israel lobby and his big-ticket domestic policy proposals have only aggravated Democrats' worries, even as they fail to coalesce around a more moderate alternative to the senator, who describes himself as a democratic socialist.

Competitors for the nomination stepped up their criticism of Sanders on Monday as the group prepared to face off Tuesday night at the 10th Democratic primary debate in Charleston. South Carolina holds its primary Saturday, and a win by the senator from Vermont – or even a very strong showing – would make it hard for one of the other candidates to catch up.

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After a landslide win in Nevada's Saturday caucuses, Sanders went on "60 Minutes" Sunday and made some complimentary remarks about former Cuban dictator Fidel Castro.

"We're very opposed to the authoritarian nature of Cuba but it's unfair to say everything's bad. When Castro came into office you know what he did? He had a literacy program," Sanders said.

That brought a torrent of criticism from not just opposing campaigns but state-level Democrats warning about the impact of such comments down the ticket.

"We already have one president who praises dictators and their mob-like tendencies; we don't need another one. As president, Joe Biden will stand up on the global stage against tyrants and fight for freedom and democracy," Cristóbal Alex, senior adviser to the former vice president said in a statement.

Former South Bend, Indiana, Mayor Pete Buttigieg added his voice, too, saying on Twitter: "After four years of looking on in horror as Trump cozied up to dictators, we need a president who will be extremely clear in standing against regimes that violate human rights abroad. We can't risk nominating someone who doesn't recognize this." The multilingual candidate made a similar tweet in Spanish.

While Sanders pointedly noted that he condemned the imprisonment of dissidents in Cuba and criticized president Donald Trump for "trading love letters" with North Korean dictator Kim Jong Un, the remarks about Castro hit hard in Florida, a swing state Democrats are eager to reclaim in November's presidential election.

Rep. Debbie Mucarsel-Powell, Florida Democrat whose defeat of a GOP incumbent helped win the Democrats their House majority, noting that she is the first South American member of Congress and represents many Cuban-Americans called Sanders' remarks "absolutely unacceptable."

Another new Democratic member of Congress from Florida, Rep. Donna Shalala, agreed.

"I'm hoping that in the future, Senator Sanders will take time to speak to some of my constituents before he decides to sing the praises of a murderous tyrant like Fidel Castro," the former Clinton administration Health and Human Services secretary tweeted.

The state party, too, took a veiled shot at Sanders.

"Florida Democrats condemn dictators who toppled democracies across the globe and stand in solidarity with the thousands of people who have fled violent dictatorships in Cuba, Venezuela and Nicaragua," Terrie Rizzo, chairwoman of the state party, said in a statement. "Candidates need to understand our immigrant communities' shared stories, as well as provide solutions to issues that matter to all Floridians including access to affordable health care and rejecting a Trump economy that works only for the very rich."

Former Democratic gubernatorial nominee Andrew Gillum, considered a rising star in the party, added his exasperated response, tweeting, "No one should have sympathies for Fidel Castro's brutal and repressive regime. Let's stay focused, Democrats."

Democrats are eyeing Florida not just for the presidential race but to keep the House majority as well. Many see Sanders' remarks as unnecessarily, and unhelpfully, alienating an important voter group in the Sunshine State. And no sooner had Sanders enraged some members of the party over Cuba then he added another issue to fight about: Israel. That exponentially upset establishment Democrats, who marveled angrily how Sanders could manage to upset two key Florida voter groups – Cuban-Americans and Jews – in a single 24 hours.

Sanders announced on Twitter he would not attend the conference of the American Israel Public Affairs Committee, a powerful pro-Israel lobby embraced by many Republicans and Democrats alike.

"I remain concerned about the platform AIPAC provides for leaders who express bigotry and oppose basic Palestinian rights, Sanders said. That brought a swift and brutal response from an interest group most candidates do not want to antagonize.

"Senator Sanders has never attended our conference and that is evident from his outrageous comment," AIPAC said in a statement. "By engaging in such an odious attack on this mainstream, bipartisan American political event, Senator Sanders is insulting his very own colleagues and the millions of Americans who stand with Israel. Truly shameful."

His campaign manager, Faiz Shakir, defended Sanders' decision, saying the lawmaker was standing up for Palestinians.

"He doesn't play political games. Bernie sees a system that doesn't respect Palestinian rights," Shakir said on MSNBC.

Sanders is also likely to take heat at the debate Tuesday night for the cost of his sweeping proposals for "Medicare for All" and free public college. He released a plan to pay for his proposals Monday night but some have criticized the plans as not generating enough to cover the costs.