The news that Senator Kamala Harris has dropped out of the race highlights the fact that the Democratic field is growing less diverse with each passing month.

It's now reached the point where a field that showed such promising diversity at first has been whittled down essentially to four people with first-tier status, and they're all white. There is diversity within than foursome--a gay man, a Jewish man, a woman. But in a party so dependent on voters of color, this is striking--and not in a good way.

Of course, there is nothing wrong with Democrats selecting a white presidential candidate to represent the party. But that should be up to the voters, and not the DNC by means of their debate inclusion practices.

Those candidates can, however strike a blow for diversity. They should band together and threaten to boycott the December Democratic debate unless the DNC and media partners agree to not exclude candidates who have shown measurable public support before the voting begins. That includes, at the very least, Cory Booker and Julian Castro, and could also include Andrew Yang and Tulsi Gabbard, who have managed to make the most recent debate stage despite long odds.

Although Harris had qualified for the December debate, her exit could create an unacceptable scenario on December 19 when the candidates gather in Los Angeles. Booker and Castro’s exclusion, coupled with the probable exclusion of other candidates of color including Yang and Gabbard, means the December debate could very well include only six candidates, all of them white. (Booker, Castro, Yang, and Gabbard have all hit the fundraising threshold, but not the polling one.)

Democrats and the DNC should be asking themselves if they really want to eliminate all the candidates of color before the first states even get to vote. And the leading candidates, all of whom are white, should do something about it.

There is precedent for the top-tier candidates banding together to protect the integrity of the debate process. Back in January 2016, NBC News, as a DNC debate sponsor, tried to bar former governor Martin O’Malley from its debate, citing his poor polling numbers compared to Hillary Clinton and Bernie Sanders. While it was apparent that O’Malley’s campaign was going nowhere, it was obvious to any objective observer that eliminating him was a choice for voters in Iowa and the other primary states to make—not NBC News.

On January 8, 2016 shortly after noon, Sanders tweeted that O’Malley should be allowed on the next debate stage. Literally one minute later, the Clinton campaign tweeted out similar support for O’Malley’s inclusion. And a few hours later, DNC Chair Debbie Wasserman Schultz tweeted that the DNC was also demanding that NBC News include O’Malley.

This joint public pressure ensured O’Malley’s inclusion. It turned out to be his final debate, but it was the voters, and not outside organizations, who chose O’Malley’s fate.

Now, it is the DNC itself that is the culprit of such unfair practices. The party has established criteria for the December debate, which will mean that Booker and Castro could both be possibly excluded from the stage.

Booker and Castro have been able to organically secure more than 200,000 unique donors each, and both have shown measurable poll support, especially with African-Americans and Latinos respectively. Excluding these two candidates of color, who represent crucial aspects of the Democratic base, from debates before Iowa could be a mistake with lasting implications for the party and country.

I personally like some of these candidates, such as Booker and Castro, while I am not fond of Gabbard. But whether I like them isn’t the point. It is not my place nor anyone else’s place to deny a candidate an equal opportunity to make their case.

Maybe there is an argument to be made for a smaller debate stage at some point, but the DNC has set up criteria that allows a billionaire to buy his spot while excluding serious candidates with a following and something to say.

And while we’re on the subject of Tom Steyer, he has spent $47 million of his own money in what amounts to a scam. Since he needs donors only to meet the DNC’s bizarre debate criteria, he has essentially purchased his donor base, through tactics such as selling $1 swag with free shipping—usually items worth far more than $1—that has nothing to do with him or his presidential campaign.

“ A debate stage that lets a white billionaire like Steyer buy his spot but excludes substantive candidates of color like Booker and Castro is neither democratic nor representative of the Democratic Party. ”

Why should he be allowed to “sell” a button about climate change or opposing Donald Trump for $1 and use that as some kind of indicia of popular support? He has also blanketed early states with enough TV ads and fancy mail to get his name identification up to the point that just enough people might utter it to a pollster because they recognize it.

Former Mayor Mike Bloomberg is eschewing debates thus far, but with his $52 billion in net worth it’s not hard to imagine clever ways for him to meet future DNC debate thresholds.

A debate stage that lets a white billionaire like Steyer buy his spot but excludes substantive candidates of color like Booker and Castro is neither democratic nor representative of the Democratic Party.

As a person of color, I hope the DNC and the frontrunners are listening. It isn’t the DNC’s place to eliminate viable candidates before voters are allowed a say. I hope Biden, Sanders, Warren, and others will step up to tell the DNC that the Democratic Party is stronger when all viable candidates are allowed to be heard.

David de la Fuente is a senior political analyst at Third Way.