Elizabeth Warren won Thursday night’s PBS/Politico debate by taking on the corruption of Donald Trump and the corruption of the Democratic Party she hopes to represent as its 2020 presidential nominee.

The Massachusetts senator delivered her message relentlessly throughout the debate. Minutes after the forum opened, she seized on a question about impeachment, recalling President Trump’s 2016 campaign promise to “drain the swamp” in Washington. “And yet he came to Washington, broke that promise, and has done everything he can for the wealthy and the well-connected, from tax breaks to ambassadorships,” she declared. “We have to prosecute the case against him. And that means we need a candidate for president who can draw the sharpest distinction between the corruption of the Trump administration and a Democrat who is willing to get out and fight not for the wealthy and well-connected, but to fight for everyone else. That’s why I’m in this race.”

Warren’s debate statement picked up on a theme she has developed in recent days, as she has sought to distinguish her progressive populist candidacy from those of more moderate Democratic rivals such as Pete Buttigieg and Joe Biden.

“Unlike some candidates for the Democratic nomination, I’m not counting on Republican politicians having an epiphany and suddenly supporting the kinds of tax increases on the rich or big-business accountability they have opposed under Democratic presidents for a generation,” Warren argued in a December 12 speech at the New Hampshire Institute of Politics. “Unlike some candidates for the Democratic nomination, I’m not betting my agenda on the naive hope that if Democrats adopt Republican critiques of progressive policies or make vague calls for unity that somehow the wealthy and well-connected will stand down.”

On the debate stage Thursday night, Warren extended that theme by distinguishing her own policies from those of her more centrist rivals. Asked about critics who say her proposed tax hikes would “stifle growth and investment,” Warren declared, “Oh, they’re just wrong!” That pronouncement drew a roar of approval from the crowd, and the cheers continued as the senator explained her proposal for a 2 percent “wealth tax” on net worth between $50 million and $1 billion—as well as a 6 percent tax on billionaires.

With those new tax revenues, she said, “we can invest in the rest of America.” And she went on to describe the ambitious social programs the money would fund.

That was too much for Pete Buttigieg, the mayor of South Bend, Indiana, who with Warren, Biden, and Bernie Sanders has emerged as a front-running contender in the early caucus and primary states that will set the standard for next year’s Democratic competition. Buttigieg referred to Warren’s approach as “extreme,” and he argued that “we’re being offered a false choice: You either go all the way to the extreme, or it’s business as usual.”

“Yes, taxes on individuals and on corporations are going to have to go up,” he said. “We can also be smart about the promises we’re making, make sure they’re promises we can keep without the kind of taxation economists tell us would hurt the economy.”

The sparring between Buttigieg and Warren was the sharpest of the debate, especially when they clashed over the financing of their campaigns. “Most of the people on this stage run a traditional campaign, and that means going back-and-forth, coast-to-coast to rich people,” said Warren, who noted recent reports that Buttigieg had held a private fundraising event in a California “wine cave,” where he was surrounded by wealthy donors.

“We made the decision many years ago that rich people in smoke-filled rooms would not pick the next president of the United States,” continued Warren. She then got off the best line of the night: “Billionaires in wine caves should not pick the next president of the United States.”

Buttigieg reprised the old argument that big money is a necessary evil of contemporary politics. “We need to defeat Donald Trump,” he said. “We shouldn’t try to do it with one hand tied behind our back.” The former mayor then took shots at his rival for her personal wealth, and for transferring money between campaign accounts, before griping that Warren was “issuing purity tests.”

That response invited a takedown from the Warren campaign. Before the debate was done, it came.

“A president was impeached last night because of corruption,” said Warren aide Kristen Orthman. “A Democratic nominee running on a defense of billionaires and lavish fundraisers in crystal wine caves, and in defense of the corrupt system that wealthy donors fuel, is a terrible risk for Democrats and very likely going to lose.”

That was rough. But no rougher than the takedown Warren delivered during the exchange with Buttigieg. In it, she did not mention the mayor by name. She simply said, “Here’s the problem: If you can’t stand up…to the wealthy and well-connected when it’s relatively easy when you’re a candidate, then how can the American people believe you’re going to stand up to the wealthy and well-connected when you’re president and it’s really hard?”

That is the problem. And on Thursday night, Elizabeth Warren addressed it more effectively than any of the other candidates.