Mike Bloomberg is preparing a massive media campaign against Bernie Sanders, whose commanding Nevada caucus victory has also drawn the attention of other top Democratic candidates -- and rankled establishment Democrats who believe that the far-left, self-avowed "democratic socialist" could alienate moderates and cost the party the White House.

CNBC first reported Bloomberg's new approach, which will employ opposition research, surrogates, and advertisements across multiple platforms. The volley began on Monday, as the Bloomberg campaign unveiled a video accusing Sanders of being weak on gun control -- an issue that Bloomberg has previously sought to corner. The former New York City mayor already has spent over half a billion dollars in campaign advertising, reports said.

The all-out blitz comes as Sanders' partial defense of Fidel Castro's brutal Cuban Revolution in an interview televised this weekend only underscored his possible vulnerabilities among Democratic moderates heading into Saturday's South Carolina primary and the 14 critical Super Tuesday contests three days later.

Additionally, Bloomberg’s campaign on Monday delayed a scheduled CNN town hall so that he can spend more time preparing for Tuesday’s debate. He was scheduled to appear on CNN on Monday, but he'll now join the network for the live question-and-answer program on Wednesday.

A spokeswoman for Bloomberg called the debate “crucial” and said, “The country can’t afford to let Bernie Sanders skate by another debate without a focus on his extreme record.” Bloomberg had his debate debut last week and his performance was widely deemed rocky and underwhelming for a candidate who has sought to give off the air of a front-runner.

The Bloomberg campaign didn't immediately respond to Fox News' request for comment.

Bloomberg won't be on the ballot Saturday, but he will compete on Super Tuesday, when one-third of the delegates will be awarded. The prospect Sanders might effectively lock up the nomination in a little more than a week has amplified concerns for Democrats who believe Sanders' liberal policies will drive away moderate and independent voters in the general election in November. South Carolina Rep. Jim Clyburn, the top-ranking black leader in Congress, warned of added risk for Democrats if Sanders were the nominee.

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“I think it would be a real burden for us in these states or congressional districts that we have to do well in," Clyburn told “This Week” on ABC.

He noted that congressional districts that helped Democrats win back the House are moderate and conservative. "In those districts, it's going to be tough to hold on to these jobs if you have to make the case for accepting a self-proclaimed democratic socialist,” Clyburn said.

Nevertheless, Sanders successfully relied on his diverse coalition of support Saturday to dominate his Democratic rivals in Nevada, pulling far ahead of second-place finisher former Vice President Joe Biden and Pete Buttigieg, the former mayor of South Bend, Ind., who came in third. Massachusetts Sen. Elizabeth Warren landed in fourth, while Minnesota Sen. Amy Klobuchar and Tom Steyer were still in a close race for fifth on Sunday.

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Sanders' new status was clear as both Buttigieg and Biden went after him harder than they have before.

In his speech to supporters in Las Vegas, Buttigieg denounced Sanders in his sharpest terms yet, changing that the senator was calling for an “inflexible, ideological revolution that leaves out most Democrats.”

"Not to mention most Americans,” Buttigieg said.

He said Sanders has shown a “willingness to ignore or dismiss, or even attack the very Democrats that we absolutely must send to Capitol Hill."

Biden, whose struggling campaign got only a slight boost in Nevada, took an indirect swipe both Bloomberg and Sanders, who is an independent and not a member of the party he's seeking to represent in November.

“I ain’t a socialist. I’m not a plutocrat. I’m a Democrat," Biden told supporters.

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However, Warren this weekend conspicuously held back from criticizing Sanders other than questioning his priorities on Senate procedure -- raising questions as to whether she is angling for a vice president spot.

Speaking to reporters in Denver, Warren wouldn’t say whether a Sanders nomination would be a risk for the Democratic Party. “I think that Michael Bloomberg is the riskiest candidate standing on that stage because of his history of hiding his taxes, his history of harassment of women and his history of defending racist policies,” Warren said in response to the question about Sanders.

She only mentioned Sanders’ name once, when she noted that they differ on the filibuster -- Warren wants to abolish it, Sanders does not.

“I think I’m the least risky candidate,” she added, citing her progressive values and record of results. Reminded that she was being asked about Sanders, Warren replied, "I heard you."

One woman in the audience asked Warren to explain the benefits of democratic socialism. Warren said: “you’ve got the wrong candidate.” Warren said she was not a socialist. “I believe in markets,” she said, adding quickly, “Markets without rules are theft.”

Separately, some Democrats are worried that the new focus on Sanders may be too little, too late. Democratic strategist James Carville bemoaned the fact that until recently, most of Sanders' opponents have largely failed to attack Sanders or draw scrutiny to his record.

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“We gotta hope that some of these candidates develop political skills quickly,” he said. If Sanders is the nominee, Carville said, “The risk in losing the election is deep and profound.” He added: “We just gotta pray.”

Indeed, Trump gloated on social media, continuing his weekslong push to sow discord between Sanders and his Democratic rivals.

“Looks like Crazy Bernie is doing well in the Great State of Nevada. Biden & the rest look weak,” Trump tweeted. “Congratulations Bernie, & don’t let them take it away from you!”

All the Democratic candidates are pledging to stay in the race through South Carolina, and some candidates were already campaigning Sunday in Super Tuesday states.

Nevada's caucuses were the first chance for White House hopefuls to demonstrate appeal to a diverse group of voters in a state far more representative of the country as a whole than Iowa and New Hampshire. Sanders won by rallying his fiercely loyal base and tapping into support from the state's large Latino community.

In a show of confidence, Sanders left Nevada on Saturday for Texas, which offers one of the biggest delegate troves in just 10 days, on Super Tuesday.

Saturday's win built on his victory earlier this month in the New Hampshire primary. He essentially tied for first place in the Iowa caucuses with Buttigieg, who has sought to position himself as an ideological counter to Sanders’ unabashedly progressive politics.

But for all the energy and attention devoted to the first three states, they award only a tiny fraction of the delegates needed to capture the nomination. After South Carolina, the contest becomes national in scope, putting a premium on candidates who have the resources to compete in states as large as California and Texas.

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That when Bloomberg, the former New York mayor who dominated the political conversation this week after a poor debate-stage debut, intends to become a factor after skipping the first four contests.

The stakes were high for Nevada Democrats to avoid a repeat of the chaos in the still-unresolved Iowa caucuses, and it appeared Saturday’s contest was largely successful.

Nevada Democrats sought to minimize problems by creating multiple redundancies in their reporting system, relying on results called in by phone, a paper worksheet filled out by caucus organizers, a photo of that worksheet sent in by text message and electronic results captured with a Google form.

Buttigieg’s campaign is raising questions about the results, citing more than 200 reports of problems allocating votes. It wants the state party to disclose more details of the votes and address concerns before releasing final results. But the party said it was not planning to offer a more detailed voting breakdown and appeared to be inviting the campaign to follow recount rules if it wanted to challenge the results.

Fox News' Paul Steinhauser and The Associated Press contributed to this report.