KEY POINTS As Sanders surges, moderate Democrats warn against giving him the nomination

Some moderate Democrats worry "socialist" label will hurt Sanders' chances

Sanders raised almost $12 million more than Biden last quarter

Sanders is currently leading in Iowa and New Hampsire

With the first state set to primary in less than a month, some establishment Democrats are fretting over Sen. Bernie Sanders’ (I-Vt.) strong polling.

Iowa voters are set to voice their choice for the Democrats’ presidential nominee on Feb. 3. Right now, per RealClearPolitics, Sanders is polling in first there. He’s also in the lead in New Hampshire and is tied with former Vice President Biden in California. Although Biden is still leading in national polling, he’s trailing in these key states – making his nomination far from a foregone conclusion.

These trends haven’t gone unnoticed by moderate Democrats. Many in this camp are strongly in favor of Biden – who has a long, proven career as a moderate Democrat – and are arguing that pitting Sanders against President Donald Trump this fall would be a disaster. However, it is also likely that the concern over Sanders is linked to his policies, which include increasing taxes on the wealthiest Americans and instituting Medicare For All.

Rahm Emanuel, who once worked as an adviser to President Barack Obama after serving as the mayor of Chicago, recently gave his own warning about Sanders in an interview with the Associated Press. “You need a candidate with a message that can help us win swing voters in battleground states,” Emanuel said, something he doesn’t believe Sanders has. He also said that Sanders’ open embrace of democratic socialism will only hurt him on the national stage.

Rep. Ami Bera (D-Calif.) has said that Sanders’ policies would make it difficult for Democrats to defend dozens of seats this fall. As the head of a team focused on supporting Democrats with vulnerable seats, Bera believes many incumbents will have “to run away from the nominee” because defending proposals like Medicare For All won’t be easy.

In general, establishment Democrats seem wary about how the “socialist” tag will play out against Sanders.

Despite these concerns, Sanders’ campaign appears to be doing very well. Although aggregate polling shows him holding firm at second place behind Biden, Sanders’ campaign recently boasted the largest fourth-quarter fundraising haul at nearly $35 million. This far outpaced Biden’s campaign, which pulled in almost $23 million in the same period.