COUNCIL BLUFFS, Iowa Massachusetts Sen. Elizabeth Warren , the first major Democratic candidate to announce a challenge to President Donald Trump , had only been in Iowa for a few hours when she laid down a marker with implications for every other Democrat who might run for president in 2020.

We ought to be building a movement, and the way we do that is with lots of involvement from lots of people, not having billionaires buy these campaigns, whether were talking about super PACs or self-funding, Warren told reporters after the first rally of her campaign, held in an event space attached to a bowling alley in this city on the Missouri River. As Democrats , in a primary, we should lock arms and make sure this is the party of the people.

Warrens call to disavow super PACs and self-funding, along with a growing movement within the Democratic Party to reject donations from Wall Street and business interests, is set to reshape how Democratic candidates bring in the millions of dollars necessary to power their primary campaigns. And its a sign that the way dozens of 2020 candidates raise their cash will be just as important as how much they bring in and how they spend it.

It also represents a continuation of two trends from the 2018 elections. The first saw Democrats collect more than $1.2 billion in online, small-dollar donations via ActBlue. The second saw more than three-quarters of newly elected congressional Democrats pledge to say no to corporate PACs, which bundle donations from a business employees and funnel them to elected officials. The performance of candidates like former Rep. Beto ORourke (D-Texas) who narrowly lost to GOP Sen. Ted Cruz established the political potency of swearing off super and corporate PACs, although not without some pushback .

Warren wont be the only candidate to discuss money in politics expect almost every Democratic candidate to make it part of their stump speech, and for Montana Gov. Steve Bullock to place it at the center of his campaign if he runs but Warrens early entry has given her a chance to set the terms of debate. The Progressive Change Campaign Committee, which has long functioned as Warrens unofficial political arm, has already begun to pressure other candidates to agree to the senators conditions.

Were hoping to create a domino effect, said Adam Green, the co-founder of the PCCC. Any outliers will stick out like a sore thumb.

This challenge is a proxy for cleaning up the Democratic brand, having it be associated with the people, not big money interests, he said. It incentivizes Democratic Party politicians to associate with regular people when theyre getting policy advice.

End Citizens United, a political action committee that rallied congressional candidates to swear off corporate PAC donations, is hoping to convince Democratic candidates in 2020 to do the same. At an event in Washington, D.C., earlier this week, four freshly elected Democrats Reps. Jason Crow (Colo.), Abigail Spanberger (Va.), Antonio Delegado (N.Y.) and Jared Golden (Maine) said the argument helped them win over voters across the political spectrum.

This should really be about powering their campaigns from the people, said Tiffany Mueller, the president of End Citizens United, which hosted the event. We think they should not have single candidate super PACs.

Many Democrats who are potential presidential candidates in 2020 have already promised to stop accepting corporate PAC donations, including Sens. Cory Booker (N.J.), Kirsten Gillibrand (N.Y.), Kamala Harris (Calif.) and former Housing and Urban Development Secretary Julian Castro. But super PACs which can raise unlimited sums, provided they dont coordinate with the candidate theyre supporting are more complicated: Theres nothing a campaign can do to stop allies from creating and funding one.