Social justice activist Shaun King insisted he isn't flip-flopping after saying he was "99% sure" he'd never support Sen. Kamala Harris in 2018, then calling her "the most progressive VP nominee in American history" on Tuesday.

"In 2018, I said I did not plan on endorsing either Joe Biden or Kamala Harris IN THE DEMOCRATIC PRIMARIES," King wrote on Twitter on Wednesday. "I endorsed Bernie. I’ve been a strong critic of Biden [and] Harris on issues of justice. She has grown and evolved on policing ]and] justice. Especially this summer."

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King, who is connected to the Black Lives Matter movement, had accused Harris of contributing to mass incarceration in 2018.

In this June 27, 2019, file photo, then-Democratic presidential candidate Sen. Kamala Harris, D-Calif., listens to questions after the Democratic primary debate hosted by NBC News in Miami. (AP Photo/Brynn Anderson, File)

"I'll be frank and tell you two Democrats that I am 99% sure I won't be supporting - primarily because of their dismal history on criminal justice reform over the course of their entire careers," King wrote on Twitter before the 2020 election cycle ramped up. "Joe Biden [and] Kamala Harris. They both helped build [and] advance mass incarceration."

Democratic presidential candidate Joe Biden tapped Harris, a former district attorney and current senator from California, to be his running mate on Tuesday.

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Neither represents the most progressive flank of the party, disappointing some left-wing activists like King.