Though Sanders and Yang differ in significant ways, they're both running anti-establishment campaigns that speak to an electorate frustrated with the status quo, wary of Democratic insiders, and looking for economic help. For Sanders, their overlapping bases may give him a small boost if Yang drops out of the race down the road or if he works to woo the so-called #YangGang.

But it’s also a potential threat to Sanders even if Yang continues polling in the single digits. If Yang shaves off a few percentage points from Sanders’ voting bloc, particularly in early-primary states such as New Hampshire, that could turn a second- or third-place finish into something worse.

“Bernie understands that the country is in crisis,” Zach Graumann, Yang’s campaign manager, told POLITICO. “There's a lot of similar urgency and messaging that comes with that.”

The intersection of Sanders and Yang supporters was highlighted last week when Sanders' former ad firm — Devine, Mulvey and Longabaugh — signed on with Yang's campaign. Mark Longabaugh, a partner at the company that produced Sanders’ famous “America” TV ad in 2016, told POLITICO that it chose Yang because “he’s offering the most progressive ideas.” The team had talks with at least one other presidential campaign about potentially working for it this cycle after splitting with Sanders earlier this year.

“He wants to transform the economy into an economy focused on people rather than corporate profits. That's the sort of progressive bedrock candidate that we're drawn to,” Longabaugh said. “Where a lot of candidates seem more negative and angry, I think Andrew comes to this displaying some optimism and a new way forward that could get this country to look to a new and better future. ”

The Sanders-Yang overlap underscores another factor in the Democratic primary: While pundits frequently opine on “moderate” and “progressive” lanes, there's also an “anti-establishment” lane in which Yang, Sanders, Elizabeth Warren, Tulsi Gabbard, and Marianne Williamson are jockeying for support.

Just as Sanders is no longer the sole progressive in the race like he was in 2016, he isn’t the only anti-establishment contender anymore, either. Sanders seems to acknowledged as much.

“I like Andrew. Polling has shown my supporters support other candidates, polling has shown that other candidates' come over to us," he told POLITICO in an interview in Iowa on Friday. Sanders urged voters upset with the status quo to examine his decadeslong record of challenging the establishment: "These ideas that I am advocating now — I think in fairness, I’ve help transform politics in America — are not new ideas to me. I was out there fighting for Medicare for All 30 years ago.”

The contest for disaffected voters could be particularly fierce in New Hampshire, where independents can participate in the primaries. Exit polls showed Sanders won independents in his first presidential bid, and expectations for him in New Hampshire are high after he defeated Hillary Clinton there by 22 percentage points in 2016. Yang has also sensed an opportunity in New Hampshire, visiting it five times in the past three months and more than 20 times total.

“There is an intensity among the supporters of Andrew Yang that is very reminiscent of the Bernie supporters of 2016,” said Ray Buckley, chairman of the New Hampshire Democratic Party. “They’re very passionate about their candidate, and they are very active online, both on Twitter and Facebook, in expressing their strong support.”

Sanders and Yang, he added, “certainly appeal to not just Democrats, but to independents as well.”

Sanders and Yang's dual fans could affect the race in Iowa, too, where caucus-goers who back a campaign that doesn't receive 15 percent of support at the site can switch to another candidate.

Yang’s aides said the entrepreneur and many of his staffers supported Sanders in the 2016 primary. They said they still think highly of him and his diagnosis of the nation’s problems. At times, Yang has publicly praised Sanders. He wished him a happy 78th birthday in September, while saying Sanders "has moved our country in the right direction and he’s not done yet.”

But as the Iowa’s caucuses approach, staff members for Yang, whose signature proposal is a $1,000-a-month universal basic income, have begun to contrast him more with Sanders.

“There are strong differences between us,” said Graumann. “We disagree over the federal jobs guarantee. We love the spirit of a $15 minimum wage, but we think that $1,000 a month would actually be more effective to accomplish the same goal.”

Sanders’ aides recently took a swipe at Yang after he distanced himself from the senator’s Medicare for All bill, though his website had previously said the country “must move in the direction of a single-payer system.” While campaigning in New Hampshire last week, Yang said quickly eliminating private insurance would be "too disruptive” but that he backs "the spirit of what Bernie is trying to accomplish."

Yang, whose site still features “Medicare for All” in its policy section, but whose team said it stopped referring to “single-payer” early this year, told reporters last week he'd be releasing a "detailed health care plan in the days ahead."

NOW: Andrew Yang clarifies position on "Medicare for All."

Yang says a health care plan that eliminates private insurance in favor of government overhaul would be "too disruptive."

"I support the spirit of what Bernie is trying to accomplish," Yang says. #nhpolitics

WATCH👇 pic.twitter.com/KDEeGAoESh

— Nicole Sganga (@NicoleSganga) October 23, 2019

“Oh come on,” Faiz Shakir, Sanders’ campaign manager, tweeted in response. “You either take on the corporate greed that rots the system, or you don’t. Millions upon millions of American lives rest on leaders having the guts to take this fight on."

Shakir said in a statement that he wishes the former Sanders admen now working for Yang “the best” and appreciates “the good work they did on the last campaign.” But he also suggested the campaign is being more innovative now by making ads themselves.

“Our in-house team is producing such great work,” he said. “I’m sure the consulting class is a little worried about this approach being successful.”

An October survey by Reuters found Sanders’ backers were three times more likely to choose Yang as their second choice than fans of Warren or former Vice President Joe Biden.

But Chris Kahn, the polling editor at Reuters, warned that those figures aren’t earth-shattering — at least not yet. Sanders, he said, is currently in no danger of losing real support to Yang, though he could peel off some voters.

“Any way you slice it, you're not you're not finding a plurality going toward Yang,” Kahn said, adding, "You see some small movements where Yang seems to be gaining a little bit better in the polls."

But many voters haven’t made their minds up yet and appear to be up for grabs.

“The diversity of choices that folks have this year, people are rather enjoying,” said Buckley. “Both the voters and the activists are really slow at making a permanent commitment.”

Laura Barrón-López contributed to this report.