It was a few months after Donald Trump was elected, and Kate Fahey, a Michigan recycling agency employee, was, like many Americans, animated by an acute sense of injustice. Republicans in Michigan managed to claim nine out of 14 congressional seats after winning only half of the popular vote – for the third election in a row.

In the cold February of 2017, in the coldest part of the state, an overflow crowd packed a town hall meeting that Fahey organized. The seeming dullness of the gerrymandering issue was no deterrence. People were upset. Even voters who did not support Trump agreed with him that the system was manipulated by politicians to keep themselves in power.

Next week, Michigan will vote on Fahey’s measure to end partisan gerrymandering in the state, in a bellwether race that began as a grassroots campaign but has recently been drenched by a gush of outside money.

On Friday, a group backed by the conservative DeVos family, whose billions are headquartered in Michigan, revealed a new gift of $1.6m to defeat the anti-gerrymandering initiative. But that is dwarfed by the amount recently committed to Fahey’s effort by liberal groups and billionaires, in a late push to carry it over the line.

Since July, Fahey’s group has received $5.5m from the Sixteen Thirty Fund, a Washington DC non-profit, and $5.1m from the Action Now Initiative, a Houston-based affiliate of the Laura and John Arnold Foundation. John Arnold is a former hedge-funder and energy trader. Other late-stage donors to Fahey include Kathryn Murdoch, wife of James Murdoch ($500,000), and Stacy Schusterman, the energy heiress and CEO ($500,000).

With the latest estimates putting total spending by both sides at $18m, the money has itself become grist for accusations.

Tony Daunt of the Michigan Freedom Fund, which is backing the campaign to retain Michigan’s current political maps, said Fahey could not now reasonably describe her group as citizen-led. “Hypocrite is too kind a description for the liars behind this sham proposal, and voters who’ve been duped by their scam have every right to be outraged.”

Fahey rejects that characterization of Proposal 2, as the measure is officially known. “This was started by citizens, the language was written by citizens, citizens defended Proposal 2, and citizens are continuing the work to talk to voters about why this reform is so important.” And with big money out to overcome those voices, Fahey said, she needed big money to help the citizens of Michigan win their fight.

For a political generation, the gerrymander has protected Republican majorities in the statehouse and sent a disproportionate share of Republicans from Michigan to Congress. Redistricting proposals are on the ballot this November in an unprecedented number of states: Michigan, Missouri, Utah and Colorado.

After Fahey began organizing in Michigan, a homegrown network sprouted. Nearly 9,000 individual donors sent cash. Thousands of volunteers fanned out to collect hundreds of thousands of signatures – enough to get proposed reform language on the midterm elections ballot in November.

Redistricting proposals are on the ballot this November in an unprecedented number of states: Michigan, Missouri, Utah and Colorado. Photograph: Brandon Marshall/Rex/Shutterstock

Voters from both parties joined in, realizing that a Republican gerrymander today could be a Democratic gerrymander tomorrow. The movement took the name Voters Not Politicians. For the first 17 months, the payroll was zero.

On a Wednesday night earlier this month, about 50 volunteers gathered to celebrate the opening of a new Voters Not Politicians office in the Detroit suburb of Southfield, Michigan, the group’s eighth office statewide.

It was a quintessential campaign office: worn green carpet, a hodgepodge of chairs, and a drop ceiling with some tiles missing. A random survey of six attendees in this overwhelmingly Democratic city turned up three Democrats, two Independents and one volunteer who called himself a Democrat who voted Republican.

Tonya Rincon, 48, an industrial electrician in the local Ford factory, said she had dressed up as Rosie the Riveter and stood outside a highway rest area on Thanksgiving weekend to get people to sign the redistricting petition.

“I believe in the cause,” she said. “It’s one of those things that once you find out about it, it’s like, ‘Really?! This is really how it goes?’”

The special guest for the evening was the journalist David Daley, whose book Ratf**ked: Why Your Vote Doesn’t Count recounts the Republicans’ wildly successful national gerrymandering plan that followed the 2010 US census.

“This is a prairie fire that is going to spark here and go across the country,” Daley told the volunteers. “The message you are sending here is going to reverberate nationally.”

Town halls, a volunteer-only signature drive and a referendum on an urgent public issue, with no party infrastructure: it might look like a perfect distillation of the democratic process. Except in Michigan and elsewhere in the US, that’s not how the process works any more.

Fahey began to hear that the group could not afford the fight it was picking.

“I obviously didn’t know how to talk to the media or anybody, and I kept getting these questions like, ‘You guys don’t have $3m, how do you think you’re going to be successful?’” Fahey recalled in a recent interview at a ribbon-cutting for a new VNP office in suburban Detroit. “And I was like, ‘We’ll figure it out.’ And I was just being honest.”

The unaccountable money in US politics that sloshes into local races and geysers out of Senate campaigns has long since flooded ballot initiatives, on issues from gun control to casinos, from legalized marijuana to charter schools. In 2016, outside groups raised and spent a total of nearly $1bn to help voters decide their local rules.

Activist groups like Voters Not Politicians might start with an artisanal financing scheme, but for any cause to challenge one power center or another, the imperative of actual financing soon becomes clear. Accepting outside money can mean the difference between being blown away by opposition TV ads and getting the message across to voters who might be getting two mailers a day from the other well-financed side.

In Michigan, when the chips are down, conservative-backed groups are used to winning big-money fights over major ballot initiatives.

In 2012, conservative-aligned groups won the two most expensive ballot battles in the state’s history, defeating a renewable energy standard ($39.8m combined spending) and a collective bargaining measure ($46.9m combined spending).

To defeat redistricting reform, the National Republican Redistricting Trust has spent at least $50,000 each in Michigan and Missouri. The Michigan state chamber of commerce, backed by energy and financial interests, has spent at least $220,000 to fight the measure, and in the two weeks before the vote, the Michigan Freedom Fund chipped in $1.6m.

After accepting a $250,000 check from the National Democratic Redistricting Committee, led by the former attorney general Eric Holder, Voters Not Politicians faced charges of partisan bias. Photograph: Paul Sancya/AP

Freedom Fund director Daunt said the group was opposing the redistricting initiative on its merits and at the behest of grassroots donors. But he declined to say how many donors or where they are from.

What sets the 2018 election cycle apart in Michigan is the source of fundraising. “Conservative groups have had a financial advantage in recent years when it comes to stale legislative races, races for governor, a lot of key races that are competitive,” said Craig Mauger, the executive director of the Michigan Campaign Finance Network, a non-profit that tracks money flows in the state’s politics. “But that’s not something that we’ve really seen this year.”

For Fahey, accepting big money, was the only way forward.

“The scary part about knowing we’re up against the DeVoses and the Koch brothers and Alec,” Fahey said last month, “is that you know that the unlimited money and the power and control they have – they have everything to lose in some ways, especially in Michigan, and they’re not going to hold back.”

Fahey said that without the support of the Action Now Initiative, Voters Not Politicians would have been unable to fight a court challenge brought against the ballot proposal in April by yet another group, called Citizens Protecting Michigan’s Constitution (CPMC), which is backed by the state’s conservative-leaning chamber of commerce.

But as Fahey discovered, big money comes with complications, too. After accepting Democratic dollars recently – in the form of a $250,000 check from the National Democratic Redistricting Committee, led by former attorney general Eric Holder – her group faced charges of partisan bias.

Fahey’s response is that her group has citizen leadership and a small-donor base extending to every zip code in the state. And she said that the Democratic money came with no strings attached and that she had warned the party not to expect her group to support its candidates.

Polls are leaning in her favor. An Epic/MRA poll last week commissioned by the Detroit Free Press found 59-29 support for the ballot initiative.

“We know the people of Michigan want this,” Fahey said. “And for us to lose because there’s a basically fake news or misinformation campaign against us to confuse people, feels inherently wrong.”