Denver mayoral candidate Jamie Giellis stumbled this week when asked on a live Facebook program what “NAACP” stands for.

Giellis was being interviewed Tuesday on “The Brother Jeff Show,” which focuses on African-American issues. Off camera, a man asked her what the acronym means.

“National African-American … ,” Giellis began, before the man told her she was wrong.

“You gonna test me on this?” Giellis asked, looking uncomfortable.

NAACP stands for “National Association for the Advancement of Colored People.” The civil rights organization was founded more than a century ago and has chapters across the U.S.

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Shay J., host of the program, asked Giellis if she knew what the NAACP did. Again, Giellis appeared caught off guard.

“Well, they do advocacy for the African-American community,” she responded. “They talk about policy. They talk about issues. They stand up for some rights.”

Then social media pounced.

“If you’re running for mayor of Denver… you might wanna know what NAACP stands for, Jamimie Gillis. Also might wanna know what they do,” wrote one Twitter user.

Giellis’ rival, incumbent Mayor Michael Hancock, called the clip, “alarming.”

Shay J. told Denver's KCNC-TV that she gives Giellis credit for agreeing to the interview, but said Giellis should’ve been better prepared.

Giellis apologized Wednesday, explaining that she “momentarily struggled to recall” when she was asked what the NAACP was, Denver’s FOX 31 reported.

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“Moments after the show, while collecting my thoughts, it came to me – the National Association for the Advancement of Colored People. I told the hosts what it stood for and apologized for my momentary lapse,” she said.