As Bernie Sanders has surged in polls and racked up victories in early states, there has been growing discomfort among many Democrats about the prospect of running this fall with a socialist at the top of the ticket. On Super Tuesday, the battle between Sanders and the Democratic establishment will be coming to a head.

After a dominant win in Nevada to go with his victory in New Hampshire and his arguable win in Iowa, Sanders seemed to be in a prime position to capture the Democratic nomination just a week ago. He had a strong lead both nationally and in Super Tuesday states, lots of money, and a vast organization.

But that’s when the party, or at least prominent members of the party, began to strike back.

[LIST: Democrats saying what a terrible nominee Bernie Sanders would be]

The first step came ahead of the South Carolina primary, when House Majority Whip Jim Clyburn endorsed Joe Biden and warned of “ down-ballot carnage ” if Democrats nominated a socialist. That endorsement proved crucial to Biden winning a crushing victory in the first state with a substantial portion of black voters, the Achilles's heel of Sanders four years ago.

Then, the floodgates began to open. Pete Buttigieg and Sen. Amy Klobuchar announced they were exiting the race and endorsing Biden. Harry Reid, the former Democratic leader, Susan Rice, who was national security adviser and U.N. ambassador in the Obama administration, and Barbara Boxer, the former California senator, also announced they would be endorsing Biden. Beto O’Rourke, who made an early exit from the primary, got behind Biden.

[LIST: Major 2020 Democratic primary endorsements]

The battle between Sanders and the Democratic establishment has been raging for years, with bitterness on both sides left over from the 2016 presidential race. Sanders fans blamed Democratic elites for rigging the primary in favor of Hillary Clinton, and a number of them stayed home. Clinton supporters, in turn, blamed the embittered Sanders supporters for helping to elect President Trump by sitting on their hands.

Asked about the growing alliance against his candidacy, Sanders just folded the news into his populist message, telling CNN on Monday night: "From day one, we have been taking on the establishment, whether it is the corporate establishment, Wall Street, the drug companies, the insurance companies, the fossil fuel industry, or the political establishment. And let me be very clear: It is no surprise. They do not want me to become president."

Going into the 2020 cycle, the Democratic National Committee rewrote the rules to try to placate Sanders supporters and reassure them that the process would be fair. Rival Democrats treated Sanders with kid gloves for much of the campaign, afraid of alienating his supporters and hoping he’d fizzle out naturally. But he did not.

As a result, as Sanders vacuumed up delegates, Democrats spent most of February in a situation similar to Republicans in 2016, with a surging candidate they were uneasy about yet unable to rally around an alternative. By lining up behind Biden ahead of Super Tuesday, Democrats are hoping, in the nick of time, to accomplish what traditional Republicans failed to do, but stopping Sanders won’t be easy, nor will it be cost free. The all-out effort to take down Sanders runs the risk of backfiring on Democrats by enraging an energetic group of voters already suspicious of the national party.