A leading progressive activist lamented Sen. Kamala Harris' departure from the 2020 race Tuesday, noting that it left only white candidates to participate in this month's Democratic debate.

"It's a sad state of affairs to have six white candidates on stage, many of whom don't necessarily speak with black women, who are the powerhouse voters -- and we're at this moment where we went from the most diverse set of candidates in the history -- certainly in my lifetime -- to an all-white stage," Aimee Allison told MSNBC's Ali Velshi on Tuesday.

Allison is the founder and president of She the People, a nonprofit dedicated to "ensur[ing] that women of color will never be taken for granted again in elections."

Her comments came after Harris, D-Calif., announced she was suspending her campaign for the party's presidential nomination, leaving a top tier of candidates that consisted of white politicians.

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With Harris out of the race, December's Democratic debate will include five white men and two white women -- former Vice President Joe Biden, Indiana Mayor Pete Buttigieg, Sens. Amy Klobuchar, D-Minn., Elizabeth Warren, D-Mass., and Bernie Sanders, I-Vt. Later Tuesday, hedge fund owner and progressive activist Tom Steyer announced that he had also qualified for the Dec. 19 debate.

"It's a sad day for Kamala Harris to exit the race and still have candidates in that primary who haven't raised as much money, who didn't qualify for the debate stage this month as she had, who don't have a discernible plan to build a multiracial coalition that will win in the states that Trump won last time," Allison said.

On Tuesday, Allison's group released a statement pointing out that the Democratic field became "much less diverse today after the only Black woman in the presidential race dropped out."

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The group also appeared to take a shot at Biden, saying that if someone like him "can run for president multiple times before becoming Vice President and a leading contender for president, we have no doubt Kamala will only rise up higher."

Harris was the biggest name to drop out of the race so far. Last month, former Rep. Beto O'Rourke, D-Texas, also exited the Democratic field.

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Velshi suggested on Tuesday that Harris was much more successful than O'Rourke, saying: "Beto O'Rourke was an idea that never actually materialized into material support. Kamala Harris did at points."