It’s a point of distinction for the independent senator from Vermont. But it could be a serious limitation to his surging presidential campaign.

Working almost exclusively from his website, Sanders has raised about $8 million so far with an average donation of around $40 — impressive enough, given how little effort he’s made. But Sanders, who has been rising fast in recent early-state polls, is missing an opportunity to capitalize on his momentum with a restive progressive base that’s been without a standard-bearer since liberal icon Elizabeth Warren declined to run.

“I frankly don’t get the restraint. I don’t believe in unilateral disarmament,” said Harvard University professor Lawrence Lessig, who said that some progressives and campaign finance reform advocates think Sanders is ruining his presidential chances by not having a super PAC. (Lessig famously founded a super PAC aimed at ending super PACs.)

Sanders faces the daunting task of finding a way to stay competitive in the Democratic primaries against one of the most potent pair of fundraisers in party history, Bill and Hillary Clinton, who are expected to count their receipts on Hillary’s behalf in the billions. The Clinton campaign says it is hoping to raise $100 million in regular donations by year’s end — and that doesn’t even count the hundreds of millions of dollars likely to flow into her super PAC.

“One million dollars is a small down payment in politics these days,” said former California state Sen. Tom Hayden, who attended a Sanders fundraiser in southern California last weekend. Sanders will have enough money to “run a credible campaign” but would need more financial support to win the nomination, he said.

On the campaign trail, Sanders makes a point of shunning big-money politics. “I don’t want money from the billionaires,” he says. He refuses to have a super PAC. His campaign has held far fewer traditional fundraisers than most candidates. There are no planned retreats or other perks for committed supporters, as has become the norm for most candidates.

In interviews, Sanders’ campaign and his allies said they have no plans to ask his donors, which include Ben Cohen and Jerry Greenfield — founders Ben & Jerry’s ice cream, who sold their company for $325 million in 2000 — to write big checks or even to raise funds on his behalf, despite the fact that Sanders has a much smaller donor network and lower national profile than other candidates.

Sanders doesn’t have much of a fundraising staff beyond his social media and digital fundraising team, many of whom worked on Barack Obama’s insurgent 2008 presidential campaign.

And although he stands to benefit from Warren supporters, who have finally accepted that the Massachusetts senator won’t pursue a White House bid, he hasn’t targeted those major progressive donors who aren’t thrilled with the idea of Clinton as the nominee.

He headlined two fundraisers last weekend in California with some Hollywood celebrities in attendance, but the events were not the big-money fundraisers that have become the norm for other 2016 hopefuls. They were more like house parties.

Mimi Kennedy, an actress who hosted one of the events at her Los Angeles home, said the event was more “Iowa-style” with about 200 people in her front yard bringing in a total of about $50,000. “This was about showing off who Bernie Sanders is,” said Kennedy, who has appeared in recent movies like The Five-Year Engagement and Midnight in Paris.

Sanders himself acknowledged at the fundraiser — as he has in interviews throughout the campaign — that “of course” he will be “heavily outspent,” adding firmly: “I don’t have a super PAC, and I don’t want a super PAC.”

In order to meet his fundraising goal, Sanders will travel sporadically to New York City, San Francisco, Los Angeles and Chicago and other Democratic strongholds in the coming months to raise cash, according to Sanders’ advisers. But the campaign does not want to spend time courting major donors or enlisting them to bundle money in the way that Clinton has with her “Hillraisers” program.

“He does not want to be the kind of candidate who builds his candidacy around going to fundraising events,” said Sanders senior adviser Mark Longabaugh.

Longabaugh clarified that the campaign is open to accepting money from billionaires as long as it’s just the maximum legal donation for any donor — $2,700. “That’s quite a bit different than Jeb Bush collecting $100 million with a super PAC,” he said.

Although Sanders’ haul is expected to be much lower than many other presidential contenders, his advisers believe they are making progress in convincing voters that they won’t be wasting their vote — and financial support — on a non-viable candidate.

“His campaign so far has knocked the socks off what anybody ever thought he would do,” Cohen, the Ben & Jerry’s founder, said in an interview.

Cohen said he’s given only $1,000 to Sanders’ campaign and an in-kind contribution of ice cream at Sanders’ campaign launch event in Burlington worth a few hundred more. He hasn’t reached the primary maximum donation of $2,700 yet, but he said he probably will.

He hasn’t hosted a fundraiser yet, but he’d be “happy to” in the future. Cohen won’t be starting a super PAC on Sanders’ behalf, but he’ll consider giving it money if Sanders gave the outside group his blessing.

“The people who are going to provide the money are going to be drawn to his policy and proposals,” Cohen said in an interview. “It’s like selling ice cream. You don’t have to ask for money. Instead of asking, ‘Do you want this ice cream?’ you say, ‘Do you want this president?’”

At the Saturday morning fundraiser at Kennedy’s house, Sanders spoke for nearly 30 minutes, addressing a range of issues from the cost of college and single-payer health care to trade, campaign finance reform and climate change before a large crowd seated in bright, yellow chairs.

“I think what’s going on is our campaign is catching fire,” he said. “It’s for one simple reason: We are telling the truth. And I think that’s what the American people want to hear. And the truth may not be necessarily pleasant, but we can’t go forward unless we have the courage to take a hard look at where we are today. And where we are today is not in a good place as many of you know we are facing immoral and grotesque levels … of income inequality.”

Betty Sheinbaun, daughter of movie mogul Harry Warner, and her husband Stanley Sheinbaum hosted another Sanders event at their mansion. But there were no Hollywood A-listers at either event: Among the attendees were “Days of Our Lives” actress Deidre Hall, “Fear and Loathing in Las Vegas” producer Richard Foos, “Sister Act” producer Cindy Gilmore Asner, filmmaker James H. Stern and actress and producer Sheila Emery.

“It’s no small achievement with all the candidates and money,” said Hayden. “He is breaking through because he is credible and has a core of committed supporters. He is perceived as a very straight talker and unlike many campaigns on the left, has credentials that are persuasive. He will probably galvanize enough money to run a credible campaign.”

Sanders, who raised more than $5 million for his last two Senate reelection bids, is a favorite of organized labor and will continue to court financial support from unions. The senator — whose top five donors since 2009 have been unions, according to data compiled by the Center for Responsive Politics — has spoken at several unions halls around the country since announcing.

Sanders’ position on outside money has also created a notable contrast with Clinton. Last Friday, while Clinton was holding three fundraising events with movie stars and television executives in Los Angeles, Sanders held a fiery town hall on income inequality in Nevada.

But Sanders donors insist their support for the senator has nothing to do with Clinton. They just believe much more strongly in Sanders’ agenda and want at the very least for him to influence the primary.

“I’m not saying anybody but Hillary,” Kennedy said. “I think she’s quite a wonderful person. But I am not sure at all what her agenda will be because of her donors. How much does money get to decide our nominee?”