Cornel West, a long-shot independent presidential candidate, named Melina Abdullah, a Black Lives Matter activist, as his running mate on Wednesday, cementing a novel ticket featuring two Black Ph.D.s whom he positioned as offering a stronger commitment to racial justice than both major parties.

Ms. Abdullah, 51, is a co-founder of Black Lives Matter Los Angeles and a professor of Pan-African Studies at California State University in Los Angeles.

Mr. West, who has taught at several Ivy League universities and helped pioneer the field of African American studies, announced his selection during “The Tavis Smiley Show,” a livestreamed talk show.

Ms. Abdullah, who has never run for office before, said she was proud to be part of an all-Black ticket and would continue her role as an activist with Black Lives Matter.

“I will never step back from that,” she said, though she pointed out that the group does not endorse political candidates. “But the agenda, the Black Lives Matter agenda of ending state-sanctioned violence, right, of building a world where our children and our people can live and walk freely comes with me into this race.”

Mr. West shrugged off criticism that his left-wing candidacy, which is polling in the low single digits, could siphon off crucial votes from President Biden in his rematch against former President Donald J. Trump. He asserted that he and Ms. Abdullah, who is Muslim, presented voters with a better alternative.

“Trump is leading the country toward a second Civil War,” Mr. West said on the show. “Biden is leading the world toward World War III. That’s the choice you have if you only are tied to the duopoly.”

Mr. Biden’s campaign referred a request for comment on Wednesday to the Democratic National Committee, which cast doubts about Mr. West’s viability.

“Despite Cornel West announcing a running mate, our view remains the same: Only two candidates have a path to 270 electoral votes, President Biden and Donald Trump,” Matt Corridoni, a spokesman for the D.N.C., said in an email. “The stakes are high and we know this is going to be a close election — that’s why a vote for any third-party candidate is a vote for Donald Trump.”

A spokesman for Mr. Trump’s campaign did not immediately respond to a request for comment on Wednesday.

Mr. West said on the livestream that he and Ms. Abdullah would use the campaign to draw attention to their fight for justice.

“We want to abolish police murder, abolish police brutality,” he said. “We want to abolish poverty. We want to abolish homelessness. We want to abolish this greed that we’ve seen organized on Wall Street and Pentagon and Silicon Valley.”