Former New York mayor Mike Bloomberg has vowed to spend what it takes from his billionaire bankroll to help Bernie Sanders win the White House if the senator secures the Democratic nomination.

But Bloomberg is also on record saying Sanders, I-Vt., has no hope of victory. “I don’t think there’s any chance of the senator beating President Trump,” Bloomberg said Wednesday.

The contradiction points to the twisted logic that is set to dominate Tuesday’s debate in South Carolina. The six other candidates onstage have about a week left to blunt Sanders’ momentum, according to analyses by rival candidates. They say Sanders is on track to emerge from the Super Tuesday primaries March 3 with an insurmountable lead in the delegate hunt.

But after giving Sanders a pass for most of the year, any attacks Democrats launch on the self-described democratic socialist could undermine the party’s chance of beating Trump in November if Sanders becomes the nominee. They also risk a backlash from voters who have repeatedly punished candidates who go negative on other Democrats in this race.

“There is always a reticence to want to get on the bad side of someone who is going to be the potential nominee and president,” said Tim Miller, who advised former Florida governor Jeb Bush when he found himself in a similar position with Donald Trump in the 2016 GOP primary. “With Trump looming, I think Democrats are going to be especially skittish to want to be seen as doing anything that is helping an absolutely loathed incumbent president.”

The result is that Sanders’ rivals have been moving gingerly to shift their messages since he swept the Nevada caucuses Saturday, winning about 34 percent of the vote and 67 percent of the national delegates. Rather than target him over the underlying concern about whether he is capable of beating Trump, they have largely been attacking him from the left, arguing that he is not sufficiently aligned with the Democratic Party’s core values.

Bloomberg and former vice president Joe Biden have circulated archival video in recent days that shows Sanders defending his votes in Congress to protect gun manufacturers from liability for mass shootings. Biden has also criticized Sanders for his past consideration of a primary challenge against “our first African American president,” Barack Obama, during the 2012 cycle.

“When it comes to building on President Obama’s legacy, Bernie Sanders just can’t be trusted,” says an online video distributed Monday by the Biden campaign.

At a rally in Denver on Sunday, Sen. Elizabeth Warren, D-Mass., went after Sanders over the more obscure topic of Senate procedure.

“Bernie supports the filibuster,” she said to loud cheers from a crowd of about 7,000 people. “I’m going to get rid of the filibuster.”

The other billionaire in the race, Tom Steyer, who is polling in third place in a South Carolina polling average by The Washington Post after spending more money on the state than anyone else, is expected to make a more targeted attack on Sanders at the debate and in paid advertising before the Super Tuesday primaries.

“Tom is going to aggressively make the economic case against the socialist policies of Bernie Sanders this week in South Carolina – in particular, that Sanders policies are bad for the country and bad for working people,” said one aide, who spoke on the condition of anonymity to discuss campaign strategy.

The rapid ascent of Sanders, who won the popular vote in Iowa and the next two contests in New Hampshire and Nevada, seems to have taken many of his rivals by surprise. They spent much of past year privately arguing that Sanders had a ceiling of support that would prevent his nomination in a party where a majority of voters consider themselves moderates.

But Sanders has shown that he can broaden his coalition from the 2016 election, winning strong support among Nevada Latinos, who previously opposed him. A broad field of rivals has made it impossible for an anti-Sanders vote to coalesce. The fact that many of them are polling below the 15 percent threshold needed to win delegates has also helped him to outperform his own popular-vote share in the election result that will matter at the July convention.

There remains significant suspense over whether Bloomberg will pivot his huge paid advertising budget, currently aimed at Trump, to go negative on Sanders. Bloomberg’s top advisers view a sustained negative attack on Sanders as one of the few remaining ways to stop him from winning the nomination, especially if Warren does not rise in the polls to take away some of his support on the left and some of the more moderate candidates do not drop out before March 3.

But the campaign has so far only pivoted with digital or unpaid messaging. Bloomberg’s campaign Monday accused Sanders of being the easiest candidate for Trump to beat and condemned him for not calling out recent vandalism against one of Bloomberg’s offices, which was sprayed with the word “oligarch,” language that echoes Sanders’ rhetoric.

“Trump himself and now the Russians are indicating that Senator Sanders is the candidate they want to run against,” Bloomberg states director Dan Kanninen said on a call with reporters. “We can’t get it done if we nominate a candidate like Senator Sanders, who has just attacked his own party.”

Other Democrats in the party have spoken out more forcefully about the danger they see presented by Sanders, who in an interview with CBS’s “60 Minutes” on Sunday praised the literacy programs of former Cuban leader Fidel Castro.

Former South Bend, Indiana, mayor Pete Buttigieg condemned those comments Monday in a tweet.

“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,” Buttigieg wrote.

Though most party strategists say it is too soon to tell whether Sanders will be able to compete against Trump in the electoral college, there is little doubt that his nomination would prove a boost to Trump’s chances of winning in Florida.

“There is no question that Bernie Sanders is the least likely Democrat to win Florida’s 29 electoral votes,” said Fernand Amandi, a Democratic pollster who worked for Obama’s successful 2008 and 2012 campaigns in the state. “Avowed socialists who have openly praised Daniel Ortega, Fidel Castro, Hugo Chávez and Nicolás Maduro don’t tend to do well in Florida.”