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".
The former vice president addressed the issue directly on Saturday because it was "the first opportunity I had to do it in a fulsome way", he told reporters Sunday, explaining that he wanted to speak in SC - where blacks account for 60% of the Democratic primary electorate - and in front of "an audience that in fact would be the most likely to have been offended by what was said".
He pointed to what he called repeated missteps, including Biden's comments on segregationists and the former vice president's recent reversal on the Hyde Amendment, a long-standing congressional ban on using federal health care money to pay for abortions.
Harris said that in the 1960s and '70s, institutions "were literally working against integration of our schools".
She was due to move on to SC, where she and Biden could expect to be pressed on their tense debate exchange. Biden told CNN's Chris Cuomo.
"He is a presidential nominee, and to say something - and again, it's not about working across the aisle, if anything I've made that a hallmark of my time in the Senate, to get big things done and legislation passed - this is about him invoking a awful power dynamic that he showed a lack of understanding or insensitivity to by invoking this idea that he was called "son" by white segregationists who, yeah, they see in him their son", Booker said.
When Joe Biden first ran for president in 1988, he was considered too liberal to win.
In returning to Iowa this week, Harris jettisoned a stump speech that centered on the vague notion of "speaking truth" and offered little clear reason for her candidacy.
Biden told CNN in an exclusive interview that aired Friday that his stance on busing was taken out of context during the debate and that he wasn't expecting Harris to attack him the way she did.
The state senator Dick Harpootlian, backing Biden, said he had heard from some voters that they felt Harris's debate attack was "disrespectful". Harris's push to sharpen her message and expand her operation is shifting the overall dynamic of the contest for the Democratic presidential nominee.
Harris, however, told reporters "we do not agree", pointing to his past criticism of busing, and said she was surprised Biden was caught off-guard by her debate stage criticism.
The campaign dynamics have shifted and become more personal since the last time Biden and Harris were in SC. They want to know what they're getting. "And that's a good thing", Biden said. Segregation persists now not necessarily as a function of legislator. Kamala Harris drew a large crowd of more than 200 during her town hall in Florence Sunday.
"I'm sorry we had to go through all this, I'm sorry at one point he tried to shift blame to me".
Awaiting Biden's Sumter speech on Saturday, Sue Catanch - a black woman who has lived in Sumter most of her life - said she supports the former vice president in part because of his proximity to Obama.
"That resonated with a lot of African Americans", he said. "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".
But some Democrats said there was still plenty of time for Biden to recover.
Sunday, though, Harris did not speak much on race-related issues and did not mention her confrontation with Biden.
Indeed, the major debate in the Democratic Party is said by the media to be how "moderate" their presidential candidate should be.