The sudden exit of Sen. Kamala Harris, D-Calif, from the 2020 presidential campaign is causing a panic among some within the Democratic Party over the remaining candidates who are participating in the upcoming debate, who are all white.

Despite qualifying for the December debate, Harris announced earlier Tuesday that she was suspending her candidacy amid sinking poll numbers and fundraising.

"In good faith, I can’t tell you, my supporters and volunteers, that I have a path forward if I don’t believe I do," Harris wrote in an email to supporters. "So, to you my supporters, it is with deep regret -- but also with deep gratitude -- that I am suspending my campaign today."

Her departure leaves only six candidates on the debate stage: former Vice President Joe Biden, Sen. Bernie Sanders, I-Vt., Sen. Elizabeth Warren, D-Mass., South Bend Mayor Pete Buttigieg, Sen. Amy Klobuchar, D-Minn., and billionaire Democratic donor Tom Steyer.

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The other candidates of color have yet to meet both requirements set by the DNC to participate in the December debate. The requirements include having at least 200,000 unique donors and reaching four percent in four DNC-approved polls or six percent in two DNC-approved early state polls.

Both tech businessman Andrew Yang and Rep. Tulsi Gabbard, D-Hawaii, have met the donor requirement to qualify for the December debate but have yet to meet the polling requirement as they each only have three polls and have until the December 12 cutoff to earn the fourth.

Sen. Cory Booker, D-N.J., has met the donor requirement but does not have any qualifying polls so far. Former Housing and Urban Development Secretary Julián Castro has not met either requirement and previously failed to qualify in the November debate.

Booker expressed on Tuesday evening that he was "a little angry" of his friend and Senate colleague's exit from the race, noting how the 2020 Democratic field began as "one of the most diverse."

"We're spiraling towards a debate stage that potentially- we're still fighting to get on it, but could have six people with no diversity whatsoever," Booker said during an interview on MSNBC. "The way this is shaping up, especially with the rules of the DNC, it is preferencing millionaires and billionaires and a lot of other things that don't ever translate into viability in Iowa."

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Liberal activists decried the potential "catastrophic" all-white debate stage amid the fallout of Harris' withdrawal, some calling it "sickening" and blaming the "implicit racism and sexism of 'electability.'"

Progressive activist Aimee Allison, who leads the group She the People, which promotes female candidates of color, called the potential debate roster a "sad state of affairs."

"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," Allison said on MSNBC.

Democratic strategist Michael Starr Hopkins called the current lack of diversity on the debate stage a "disaster" for Democrats and suggested that the DNC's own debate rules inadvertently determined the potential outcome.

"The DNC thought it would help progressives demonstrate support, but it ended up hurting campaigns like Harris, Booker, and Castro," Hopkins told Fox News. "Instead of focusing on building infrastructure, they had to spend insane amounts on donor lists to get on the debate stage."

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Hopkins, who previously served as press secretary for former congressman John Delaney's presidential campaign, explained how the DNC's growing donor requirement for the debates have "devastated" many of the campaigns since the lower-tiered candidates have to allot a substantial amount of spending on access to donor lists in order to find potential donors that could aid their debate qualifications.

He also stressed how "problematic" it will be if voters of color don't see candidates of color on the debate stage.

"African Americans and people of color are the base of the Democratic Party and it’s problematic to not have a single candidate on stage that represents the diverse constituency of the Democratic Party," Hopkins said. "It could certainly affect turnout."

Fox News' Alex Pappas and Sam Dorman contributed to this report.