Warren did not name names, but her comments were an implicit rebuke of Pete Buttigieg, Joe Biden, and Kamala Harris. All of them have raised millions at fundraisers with the wealthy, a common practice in both parties.

Warren and Bernie Sanders have spurned fundraisers for the primary and the general election, calling them inherently corrupt. Warren and Sanders have both galvanized supporters with their approach, while still out-raising all of their opponents last quarter with robust small-donor, online-focused donor operations.

Warren held fundraisers in her previous campaigns for Senate. Some of that money gave her a multi-million-dollar head start in the presidential race, and some of her critics privately bristle at what they call her newly-sanctimonious approach. But at the outset of her presidential bid, Warren disavowed the practice, a move seen as a sign of desperation at the time and mocked by some of those same critics but which has paid off handsomely for her.

Warren’s comments are also something of a warning shot to any candidates save Sanders who may be tempted to attack her Tuesday night and try to halt her rise in the polls. Over the past week, Biden derided any candidate who is a “planner” rather than a doer. Buttigieg said that “it’s not a time for purity test” and debuted a digital ad attacking Sanders and Warren for their support for Medicare for All.

Buttigieg also suggested that Warren and Sanders' no-fundraiser approach would make them less electable in an election against Donald Trump. “[W]e're not going to beat him with pocket change," adding that Democrats "need the full spectrum of support in order to compete," he told Snapchat .

Buttigieg has been an unlikely favorite of the Democratic donor class, setting the pace with fundraising events. But he has had more success with small-dollar fundraising than Biden and Harris. Buttigieg's average donation hovered at $32, just $6 more than Warren's average amount, $26.

Warren’s challenge to disclose more about donors and fundraisers is most clearly directed at Buttigieg since he does not publicly disclose a full list of its bundlers. He also does not provide the time, place, and hosts of all of his fundraisers. The campaign has confirmed public reports of those involved in its “investors circle," and the dates and locations for some of its private, high-dollar fundraising events.

Harris does not list all information about her fundraisers but has released a list of members on her finance committee. Biden allows reporters into all of his fundraisers but does not currently disclose the members of his finance committee.

As questions about the influence of wealthy donors have come up in recent months, some campaigns have pushed back against Warren by pointing out that she transferred over $10 million from her 2018 Senate re-elect fund. That campaign had strong grass-roots fundraising but also raised millions through the same high-dollar fundraisers she's now denouncing.

Warren’s Medium post also laid out a number of other commitments to try to limit big money and burnish her progressive credentials.

She followed Sanders in pledging to ban corporate contributions to the Democratic National Convention next summer in Milwaukee, a $70 million-plus event that the party is currently soliciting donations for through corporations and lobbyists. Warren’s campaign did not comment on whether she would make the party return the corporate or lobbyist contributions they are currently soliciting. Sanders’ campaign has warned the DNC and potential donors that it “is under no obligation to fulfill any transaction with a corporation trying to corruptly buy access.”

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Warren also promised to reject contributions over $200 from “executives at big tech companies, big banks, private equity firms, or hedge funds." Her campaign said it will identify any such people who have already donated and return those contributions. Asked to clarify the meaning of “executive,” aides said they would “cross-check the leadership team for each company with what they post on their own websites.” Asked for clarification, the campaign did not respond.

Warren also laid out her plan to overhaul campaign finance rules. Some parts — such as pledging to not give foreign ambassadorships to donors — she previously proposed. Warren did, however, call for lowering individual contribution limits to candidates from $2,800 to $1,000, and to $10,000 to political parties. And she proposed combining that with a publicly-financed, small-dollar matching program in which the federal government would provide a six to one match for any donation under $200.

Warren vaguely wrote the plan will be paid for “by penalties coming from corporate malfeasance and major tax crimes.”

Warren’s plan is not as far-reaching as Sanders’, which calls for mandatory public financing for federal elections and replacing the Federal Election Commission with a Federal Election Administration that would empowered to impose civil and criminal penalties.

Still, Warren has made the influence of money in the political system the centerpiece of her candidacy.

“Whatever issue brings you to politics — whether it’s climate change or gun violence, student loans or prescription drug prices — there is a reason why our country hasn’t been able to make progress,” she wrote. “Corruption.”

Maggie Severns contributed to this report

