The Booker and Castro campaigns say Harris’ announcement triggered an outpouring of financial support for them. Booker had the best online fundraising day of his campaign on Wednesday, and Castro had the best fundraising day of this quarter on Tuesday. But that momentum is unlikely to earn them a lectern at the upcoming debate, as both candidates have little chance of reaching the 4 percent threshold in four approved polls before next Thursday’s deadline.

At a campaign stop in Des Moines, Iowa, on Thursday morning, Booker opened his address by praising his “friend” Harris as a barrier-breaking politician whose candidacy he said inspired black youth. But at the same time, he blasted the system that he said caused her to end her campaign before a single vote was cast.

“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. “Voters did not determine her destiny.”

“I cannot tell you how much I believe in our primaries. And I’ve seen folk here in Iowa belie what all the predictions are and show us what real viability is,” Booker added, implicitly criticizing DNC rules that factor polling and grass-roots fundraising into who can qualify for the debates. “It was this state that set a trajectory for the first black man in American history to become president — and, frankly, somebody that was way behind Hillary Clinton right now in the polls [at] that time.”

Later Thursday, Castro will host a campaign call with reporters to discuss the state of the presidential primary and Democratic debates. In a fundraising email Wednesday, he, too, criticized the DNC’s debate rules for hurting candidates of color and disenfranchising minority voters.

“[W]ith the news of Senator Harris dropping out of the race, there are currently no candidates of color who have met the DNC’s requirements to qualify for the next debate,” Castro wrote. “This process needs to be fixed.”

Even Tom Steyer, the billionaire environmentalist who has spent more than $60 million since launching his campaign in July, called for the DNC to “open the debate requirements for January so that more candidates can participate.”

“One of the strengths of the Democratic Party is that it represents every community in our great nation,” he said in a statement Wednesday. “In order to defeat Donald Trump, Democrats need to engage voters from every part of the country, and that means making sure voters hear from a diverse group of candidates before they select our nominee.”

Despite the criticism from candidates, no campaigns have recommended an alternative set of criteria for debates.

In a statement to POLITICO, the DNC defended its process, which allowed up to 20 candidates to participate in the first two set of debates and has had at least 10 candidates on every stage so far.

“This has been the most inclusive debate process with more women and candidates of color participating in more debates than billionaires,” DNC spokeswoman Xochitl Hinojosa said. “While we are legally required to have objective criteria for each debate, our qualifying criteria has stayed extremely low throughout this entire process.”

December’s qualification criteria included having 200,000 unique donors and at least 4 percent support in four approved polls.

“Nobody who has failed to reach 4 percent at this point in the race has gone on to be the nominee, and our debate criteria reflects that,” Hinojosa said. “In addition, we have made diversity a priority by requiring that every debate have women and people of color as moderators. We’ve never seen a political party take this many steps to be inclusive.”

Booker, whose campaign has shifted resources in a so-far failed effort to boost his polling numbers, made a direct plea Thursday.

“I’m here to ask for your support,” he told the audience, who applauded and briefly chanted “Cory! Cory!” “Hold on, let me be more blunt: I’m asking you when your caller ID is showing that some pollster’s calling you, pick up the phone and answer, please. Choose me. Choose us.”