Democrats are desperately rallying behind former Vice President Joe Biden in an attempt to stop Sen. Bernie Sanders from winning the nomination, Fox News contributor Karl Rove said Tuesday.

“Let’s be clear, this is not moderates. These are traditional liberal Democrats who realize their party is about ready to be taken over by a socialist and they’re going to do everything they can to stop him,” the former White House deputy chief of staff told “America’s Newsroom.”

“They realize they have no other choice,” Rove said.

O'ROURKE ENDORSES BIDEN AT DALLAS RALLY ON EVE OF SUPER TUESDAY, AS EX-VP APPEARS TO OFFER GUN-CONTROL ROLE

In a surprise moment at the end of his Dallas rally on the eve of Super Tuesday, Biden called former Texas Rep. Beto O'Rourke up to the stage -- and vowed to put O'Rourke, who has said the government should forcibly seize assault rifles from Americans, in charge of gun-control efforts.

Also at the rally, Biden accepted the endorsements of onetime rivals Pete Buttigieg and Amy Klobuchar, as the Democratic Party's moderate wing rallied behind Biden to challenge anti-establishment front-runner and self-described "democratic socialist" Sanders, I-Vt.

"Ladies and gentlemen, tomorrow, March 3, 2020, I will be casting my ballot for Joe Biden," O'Rourke announced to applause at the rally's conclusion.

O'Rourke called President Trump an "existential threat" to "free and fair elections," and urged rallygoers to view Biden as the "antithesis of Donald Trump," someone who is "decent, kind, caring and empathetic.”

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Responding to the new wave of support for Biden, Rove said Democrats are realizing that no other candidate has caught on with voters.

“Buttigieg didn’t catch on, Klobuchar didn’t catch on, earlier candidates didn’t catch on and so, who is the one person left in the fight who looks like they’ll be able to stop Bernie? It’s Joe Biden," he said.

Biden currently trails Sanders by just eight pledged delegates (56 to 48) in the race to get the 1,991 necessary to secure the Democratic Party's nomination at this summer's convention in Milwaukee. Party leaders had feared that the splintering moderate vote would allow Sanders to rack up victories in a series of high-stakes Super Tuesday contests and possibly gain an insurmountable advantage in the delegate count.

Fox News’ Gregg Re, Samuel Chamberlain contributed to this report.