COLUMBIA, S.C. — Democratic presidential candidates Joe Biden and Kamala Harris are circling each other again — this time in South Carolina, a crucial early-voting state that will test the depths of their support with black voters.

As they travel across the state in the coming days, the former vice president and the California senator probably will be pressed on their tense debate exchange over race and federally mandated school busing. Though the issue is not at the forefront of the 2020 primary, it could resonate in a state with a complicated history with race and segregation.

Several Harris supporters in the state said her pointed and personal critique of Biden, who opposed busing mandates in the 1970s, struck a chord in South Carolina. Marguerite Willis, a recent Democratic candidate for governor, said that when Harris spoke in last month’s debate about her own experiences being bused as a child, the entire room where Willis was watching the debate grew quiet.

“Growing up here in South Carolina, that’s meaningful to us,” she said. Schools were segregated when she was a kid, and she recalled not meeting a black girl her age until leaving the state for college. “So when she talked about being bused, it was powerful for me and I’m sure it’s powerful for a lot of people here who have experiences of their own.”

Though South Carolina’s primary is more than seven months away, Biden and Harris appear destined for a showdown here. Their campaigns are banking on the backing of black voters to secure the nomination, and South Carolina is the first state on the primary calendar that will test their standing with this crucial constituency.

Biden, who has decadeslong political relationships in the South, was beginning a three-stop swing in South Carolina on Saturday, with scheduled visits to Sumter, Orangeburg and Charleston. On his third trip to the state since he entered the race in late April, he intended to stress the eight years he served in the White House with Barack Obama, the first black president, and the significant change for the good that he said has taken place in the country since the 1970s. “I’ve worked to make that change happen, and yes, I’ve changed also,” he said in remarks prepared for his Sumter stop.

Harris, who planned appearances in Florence, Hartsville and Myrtle Beach, has spent more time in South Carolina than any other state in the early primary landscape. This weekend marked her ninth trip here as a presidential candidate.

The campaign dynamics have shifted and become more personal since the last time Biden and Harris were in South Carolina.

In the debate, Harris was unrelenting in her criticism of Biden, both his views on busing and favorable comments he made about working with segregationists serving in the Senate.

Biden told CNN in an interview that aired Friday that he “wasn’t prepared for the person coming at me the way she came at me,” noting that Harris knows him and his son, Beau, who died of brain cancer in 2015.

State Sen. Dick Harpootlian, who is backing Biden, said he did not believe that the issue would move voters, and that he has heard from some that they felt Harris’s debate attack was “disrespectful.”

“I think it resonates with younger voters who get all their news off Twitter or Facebook. It’s an echo chamber,” Harpootlian said, adding that he believes the state’s primary voters will be older and heavily African American. “Those are Biden’s guys, his men and women. … They want to know what they’re getting. They don’t want a promise of what’s to come in the future.”

“She can’t build herself solely on tearing Joe Biden down,” Harpootlian said. “She took that shot. What’s she offering?”

Harris muddied the debate over busing during a recent campaign swing in Iowa, appearing to tell reporters she currently opposes federally mandated busing to address school segregation. Her campaign disputed the notion that she was backtracking from her position during the debate, arguing that she supported busing in the 1970s — when Biden opposed it — but believes conditions now make it an issue to be decided by local school districts.

The technicalities of those arguments mattered little to J.A. Moore, a South Carolina state representative who is backing Harris and felt a personal connection to her story. Moore said his Aunt Loretta, who called him during the debate, was among an early group of black students to integrate a high school named for Strom Thurmond, a segregationist senator.

“That resonated with a lot of African Americans,” he said. “African Americans in South Carolina have been marginalized, have dealt with all kinds of discriminatory practices.”

For Willis, it may just be that Biden’s political time has passed.

“My view on it is that Joe Biden has had his day,” said Willis. “He’s a good man. I don’t think he’s a racist, personally. But I think that many people can beat Donald Trump and I don’t think we have to have necessarily an old, white guy to do it.”

State Sen. Marlon Kimpson, a member of South Carolina’s Legislative Black Caucus who will host Biden for a town hall meeting in Charleston on Sunday, said candidates’ past positions matter as voters weigh who is best positioned to defeat Trump.

Kimpson, who has not endorsed a candidate, said: “It’s one thing for people to get up and talk about what they’re going to do, but one of the barometers for someone espousing what their plans are is to look at what they’ve done in their past.”

Summers reported from Baltimore.