What began as a progressive pipe dream – that a rabble-rousing senator from the nation’s second least populous state could wrest the Democratic presidential nomination from one of the most well-known politicians in recent history – is starting to seem plausible.



By way of massive rallies, grassroots politicking and a record-setting number small donations, Vermont senator Bernie Sanders is winning over progressive voters, convincing them that his underdog campaign has a fighting chance against Hillary Clinton’s well-oiled – and extraordinarily well-funded – political machine.



On Thursday, the Sanders campaign announced it raised $15m since 30 April from 250,000 donors, many of whom have made small contributions online. In contrast, Barack Obama attracted only 180,000 donors during the first quarter of his presidential campaign in 2007, which has been considered the benchmark for online fundraising by an insurgent candidate in modern presidential politics.



The senator, propelled by a groundswell of support, is also gaining ground on Clinton in polls emerging from across the early voting states.



In Iowa, Sanders’ support has soared. A Quinnipiac poll released on Thursday found that 33% of likely Democratic primary voters prefer Sanders, which brings him within 19 points of Clinton, who is polling at 52%. In May, the same poll showed Clinton leading Sanders by 45 points. And in New Hampshire, Sanders trailed Clinton by just 8 points, according to the latest CNN/WMUR poll.

But while Sanders continues to gain momentum and money, political observers remain wary of whether the unkempt septuagenarian socialist can actually defeat Clinton in the era of almost unlimited campaign spending, or whether Democratic voters are just enjoying what one political operative in New Hampshire this week called “a summer fling”.

Taking advantage of a rising populist tide

Sanders is not just persuading progressives to open their wallets: he has a rabid fan base showing up to campaign events as well, drawing larger-than-expected crowds across the country. At a rally on Wednesday night, Sanders sounded almost taken aback by his welcome – nearly 10,000 supporters attended the Veterans Memorial Coliseum in Madison, Wisconsin, to hear him speak.

“Tonight we have made a little bit of history,” Sanders, 73, told the crowd. “Tonight we have more people at any meeting for a candidate of president of the United States than any other candidate.”

One attendee at Sanders’ rally in Madison, Doug Fritsch of nearby Lake Mills, told the Guardian that he was drawn to the senator because Sanders “still sees a role for government to protect the lower and middle class”. In contrast, he said he views Clinton as aligned with “more of the corporate interests”.

Fritsch said he was impressed with the “enthusiastic” crowd at Wednesday’s rally, which he saw as an effort to “a grassroots movement working” for Sanders.

But Sanders isn’t just holding big rallies either: he is spending significant time in early primary states and has already spent 15 days in the first-in-the-nation primary state of New Hampshire alone – more than any other Democratic candidate.

Adam Green, co-founder of Progressive Change Campaign Committee, a group that has hailed the Massachusetts senator Elizabeth Warren as its “north star”, said that Sanders is hitting the right notes for his left-wing base with ideas on how to unburden college students from massive debt and tackle wage inequality – and that Clinton would be wise to pay attention.

“Bernie Sanders is smartly taking advantage of the rising economic populist tide,” Green said. “And the path to success for Hillary Clinton is to be bold and populist in her campaign platform.”

Big crowds – but bigger dollars

Sanders’ campaign has evolved from a longshot ideological crusade to a legitimate operation in a very short period of time. The campaign essentially “started from scratch” in April when the senator made up his mind to run, said Tad Devine, a senior adviser to Sanders. Devine said the big-rally strategy has helped the candidate start building out a campaign network. So far, he said, everyone has been “pleasantly surprised” at Sanders’s reception.

“That style of campaigning, where there’s a give and take with voters, where people come into an atmosphere where they can almost be in a community setting, that’s something that Bernie’s very comfortable with,” Devine told the Guardian. “We don’t have time to try to do the things that we’re not adept at doing.”

But harnessing the senator’s momentum to pose a meaningful threat to Clinton will remain a challenge.

On Wednesday, Clinton’s campaign announced that she has raised an estimated $45m since declaring her candidacy in April.

“Many people doubted whether we could build an organization powered by so many grassroots supporters,” Clinton campaign manager Robby Mook said in a note to supporters on Wednesday. “Today’s announcement proves them wrong.”

Clinton’s campaign said details about who has donated to her campaign are not yet available. A full accounting of her donations, as is the same for all candidates, is due on 15 July in a filing to the Federal Election Commission.

We don’t have time to try to do the things that we’re not adept at doing. Tad Devine, senior adviser to Bernie Sanders

The Democratic frontrunner’s campaign has been heavily focused on raising money. Clinton headlined 58 different fundraisers in 18 states since declaring her candidacy in April. In contrast, she has held relatively few public events – and small ones at that – and has yet to draw crowds of the same magnitude as Sanders. Clinton’s one major rally in Iowa drew fewer attendees than a nearby Sanders rally two days later; even Clinton’s formal campaign launch in New York City was approximately the same size as Sanders’s lakeside announcement in Burlington, Vermont.

The former secretary of state often communicates her policy positions via Twitter, rather than speaking to reporters or voters. While Sanders held a question and answer session on Thursday with over 100 voters in the gritty industrial city of Fort Dodge, Iowa, Clinton spoke at a private fundraiser in Provincetown, Massachusetts, a resort town on Cape Cod.

Clinton will also get help from the Priorities USA Super PAC, which is backing her candidacy despite a pledge by the candidate to combat “uncontrolled money” in politics, and announced Thursday that it has raised $15.6m – bringing the coffers of her campaign and its allies beyond $60m so far.

In contrast, Sanders, who rails against the “grotesque and obscene” concentration of wealth in America, has refused to have a Super Pac support him and is focused on wooing small-dollar donors.

Harvard University professor Lawrence Lessig, who founded a Super Pac to end Super Pacs, said Sanders’ renouncing Super Pacs is tantamount to “bringing a knife to a gunfight”.

“I regret the fact the Bernie Sanders has embraced the idea that he’s going to live life like the Vermont snow, as pure as he possibly can, while he runs for president, because it weakens his chances – and he’s an enormously important progressive voice,” Lessig said.

That he will be outspent, Sanders admits, almost gleefully. That it will hurt his chances of securing the Democratic nomination, the upstart candidate disagrees.

“They may have the money but we have the people,” Sanders told the crowd in Madison on Wednesday. “And when the people stand together, we can win.”