DES MOINES — Senator Cory Booker came to Iowa on Thursday with a question, one that voters, activists and disgruntled members of the Democratic National Committee are also asking in the wake of Senator Kamala Harris’s sudden departure from the 2020 race.
In a year that began with the inauguration of the most diverse class of House Democrats in history, and quickly built to the most diverse field of presidential candidates in history, do Democrats want an all-white slate of top-tier candidates to be the face of their party in 2020?
“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?” Mr. Booker asked a crowd here Thursday morning. He added that Ms. Harris left the race “not because Iowa voters had the voice. Voters did not determine her destiny.”
With Ms. Harris out and Mr. Booker, the former housing secretary Julián Castro, Representative Tulsi Gabbard of Hawaii and the businessman Andrew Yang yet to qualify for the December debate, and former Gov. Deval Patrick of Massachusetts too late an entry to have a real shot at that stage, the Democratic primary is facing a reckoning over diversity, fairness and representation in the primary process. Two weeks before the December debate, which is likely to feature an entirely white roster, the criticism has centered on the qualification rules, which are tied to numbers of individual donors and poll results.
Mr. Booker, who represents New Jersey, focused on these issues in his speech here, and has been addressing them with renewed frequency all week.
Both he and Mr. Castro have seen an increase in fund-raising in the days since Ms. Harris left the race. The Booker campaign said that Wednesday was its biggest online fund-raising day of the race, with 11,000 new donors. Mr. Castro had his best fund-raising day in four months on Tuesday, pulling in roughly $200,000 in online donations.
Still, given the polling requirements, it is extremely unlikely that either man will make the December debate stage. Inside Democratic circles, there is a growing sense of unease that those rules, set by Tom Perez, the chairman of the Democratic National Committee, have disproportionally impacted candidates of color.
“We have a system designed by our own Democratic National Committee that is not in any way intended to elevate the most qualified candidate but designed to elect the person with the most money or most access to it,” said Representative Marcia L. Fudge of Ohio, who was a supporter of Ms. Harris. “That’s why you’re going to see an all-white debate stage.”
Underpinning Democrats’ apprehension in the wake of Ms. Harris’s exit is the growing schism in the party between those who prefer a moderate status quo candidate and an activist energy for a new order that features diverse leadership. Yet the current standard bearers for both factions are white candidates.
Some Democrats fear that an all-white debate stage later this month, or worse, an all-white final tier of candidates battling it out through months of primary contests, could undercut the party’s much-touted image as a bastion of diversity in the Trump era.
For a Democratic electorate wrought with anxiety about defeating President Trump in November, the possibility of fracturing support among key minority voting groups who powered the gains in 2018 looms as an existential threat — though some prominent Democrats note that the candidates of color in the 2020 field have so far failed to cultivate significant support from black and Latino voters.
On Thursday, Mr. Booker focused mostly on the threat he believes the party faces if the demographics of its candidates do not reflect its voters.
“This is not about one candidate,” Mr. Booker said in his speech Thursday. “It is about the diverse coalition that is necessary to beat Donald Trump.”
Mr. Castro has been similarly critical this week.
“By not having anyone of color onstage, the party loses a lot,” he told reporters after a fund-raiser in Los Angeles on Tuesday. “The party also loses partly the ability to inspire and excite constituencies that we need to win in November 2020 against Donald Trump. And, you know, the D.N.C. ought to do some soul searching on these thresholds.”
The grievances about who will or won’t qualify for upcoming debate stages center on the result rather than the process that led to it. Mr. Perez announced the summer debate qualification thresholds in February. Party officials informed the campaigns weeks later that debate qualification thresholds would rise as the campaign progressed.
“Our process has resulted in more women and candidates of color participating in our primary debates than billionaires,” said Xochitl Hinojosa, a committee spokeswoman. “No one who has failed to reach 4 percent at this point in the race has ever gone on to be the nominee. Our debate criteria reflects this.”
Leah D. Daughtry, a longtime Democratic National Committee member who sits on the party’s rules committee, said she’s had a number of conversations in recent days with other members about how to change the system to include more candidates of color. No one has come up with a workable solution.
“I don’t know how you fix it now without upsetting the apple cart,” she said. “But it’s a problem. It’s a real problem.”
Some prominent Democrats say the party cannot be blamed for the failure of candidates of color to make the stage, placing responsibility on their inability to build momentum for their efforts — particularly among black and Latino voters.
A growing number of voters, especially younger black voters, have rejected the notion that mere representation equals the kind of change the Democratic base is hungry for. Polls have consistently shown the former vice president Joseph R. Biden Jr. leading among African-American voters, while Senator Bernie Sanders of Vermont is widely popular among Latinos.
“When people make the case that the standards and requirements should be lowered so that candidates of color can make the debate, as a Latina, I find that insulting,” said Maria Cardona, a former D.N.C. official. “The reason why the candidates right now are the ones at the top of the polls are because these are the candidates who are getting the majority of support from, guess who, voters of color.”
Some party officials see the discussion about minority representation in the debates as inherently self-serving. Ms. Harris had qualified for the December debate but chose instead to drop out, they said.
“The D.N.C. announced their rules months ago. And I think anyone who decided to run understood that the party had rules,” said Donna Brazile, the former interim head of the committee. “I don’t know how you can blame the party for that.”
That is not how Mr. Booker and Mr. Castro see it.
Indeed, within hours of Ms. Harris’s announcement on Tuesday that she was suspending her campaign, Mr. Booker went on MSNBC, saying he was “a little angry, I have to say.”
“The way this is shaping up, especially with the rules of the D.N.C., it is preferencing millionaires and billionaires and a lot of other things that do not ever translate into viability in Iowa,” Mr. Booker said on Tuesday night.
Following Ms. Harris’s exit, prominent Democrats joined the growing chorus of support for Mr. Booker and Mr. Castro, not in outright endorsements of their candidacy, but for the need to continue to hear from a diverse set of candidates in the debates.
“Many good candidates have qualified,” Andrew Gillum, the former Democratic candidate for governor in Florida and a rising star in Democratic politics, wrote on Twitter. “But our diversity is our strength & our debates must reflect that fully.”
Mr. Gillum included links to donate to both Mr. Castro and Mr. Booker’s campaigns. Several other high profile Democrats made similar pleas on social media, leading to some surge of small-dollar support for both candidates.
Ms. Harris’s decision to drop out ignited long-simmering complaints about the primary process. But for months, some candidates and activists have been critical of a system that, they said, is heavily tilted toward predominantly white populations and was stifling the party’s historically diverse field of candidates.
A frustrated Mr. Castro, after missing the polling threshold for the November debate, decried the outsize roles of Iowa and New Hampshire, with their primarily white electorate.
Mr. Booker, who is set to barnstorm Iowa for the next four days, instead praised the state on Tuesday as the one who selected Barack Obama and set the path for the first black president.
It’s a note that has become central to Mr. Booker’s push to make the debate stage, and win the Democratic nomination.
In Des Moines, he directed these future Iowa caucusgoers to ignore the outside forces shaping the primary field.
“I want you to know that we are a nation right now that has an election to decide,” Mr. Booker said. “And Iowa, do not let anybody else decide it for you.”
He continued: “When you hear people say it’s the most important election of our lifetimes, turn around and tell them: ‘Act like it.’”
Reid J. Epstein contributed reporting from Washington.