Columbia, S.C. (CBS NEWS) – On the steps of the South Carolina State Capitol, Senators Cory Booker and Bernie Sanders on Monday joined local leaders of the state NAACP chapter and called for an end to racial injustice. Only one of them leveled a direct, personal attack on President Trump.

"We now have a president of the United States who is a racist," Sanders, an independent senator from Vermont, told the crowd, adding later, "What a president is supposed to do is to bring us together. And we have a president intentionally, purposefully trying to divide us up by the color of skin, by our gender, by the country we came from, by our religion."

Speaking just before Sanders at a Martin Luther King Jr. Day event, Booker, a Democrat representing New Jersey, didn't go as far, preferring instead to echo a popular refrain of former President Barack Obama, who liked to remind crowds that King "talked about the arc of the moral universe bending towards justice. But it does not bend with inevitability. We must be the arc-benders."

"This is not a time for us to rest in our country," Booker added. "The work is not done. The dream still demands."

South Carolina hosts the third contest in the 2020 Democratic presidential primary calendar. It will also be an important test of which candidates can appeal to a key constituency in the Democratic Party: African-American voters, who in 2016 made up 61 percent of the Democratic primary voters in that state, according to CBS News exit poll data.

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