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DES MOINES, Iowa — Presidential candidates Julian Castro and Senator Cory Booker railed against the DNC Thursday for a qualification process they said is excluding them from the December Democratic debate stage.

On a phone call with reporters Thursday, Castro said, “I did not expect the DNC to raise the threshold so close to the Iowa caucuses,” in reference to the qualification changes the DNC made for the December debate.

Both Castro and Booker criticized the process, saying it allows for billionaires to “buy their way in,” in reference to candidate Tom Steyer, who has qualified for the debate.

“Anybody without the resources to self-fund is at a disadvantage,” Castro said. “The DNC should evaluate the threshold with regard to number of donations, and also think about how we’re going to ensure that the future of our politics doesn’t just belong to billionaires who can self fund campaigns.”

To voters at an event in Des Moines, Booker said, “there’s more billionaires in the race than there are black people.”

The two candidates said Senator Kamala Harris’ exit from the race shed a light on the lack of diversity in the field, especially if they do not end up qualifying for the debate.

“What message is that sending, that we heralded the most diverse field in our history, and now we’re seeing people like her dropping out of this campaign, not because Iowa voters had the voice,” Booker said.

Castro said that is partially a result of what he calls a broken primary system. The former HUD secretary has criticized Iowa’s first-in-the-nation status before, and doubled down.

“We need to change the whole game. There’s no reason that Iowa and New Hampshire, that hardly have any black people or people of color, should always go first in nominating a president,” he said. “There’s no reason that a caucus system that makes it harder for working people, and people with disabilities to participate should be what we begin with. We need to work to reform, how we elect a president in the first place.”

While the two Democrats said they’re concerned about dwindling diversity, some Republicans mocked that fear online.