Democratic presidential candidate Joe Biden has refused to apologise for reminiscing on his work with two long-dead racist senators.
But amid a firestorm of criticism, the ex-US vice-president said he had “detested” the views of late senators who favoured separating the races.
His rivals have decried him for saying senators once “got things done” with “civility” with the segregationists.
The former US vice-president is currently leading opinion polls.
The row began on Tuesday night when Mr Biden fondly recalled his working relationship after joining the Senate in the 1970s with two southern Democratic senators, Mississippi’s James Eastland and Georgia’s Senator Herman Talmadge.
“He never called me ‘boy,’ he always called me ‘son,'” Mr Biden said at a fundraiser in New York City.
But some of his rivals among more than 20 Democratic candidates in the 2020 field pounced on his remarks.
New York Mayor Bill de Blasio, California Senator Kamala Harris and New Jersey Senator Cory Booker lambasted Mr Biden and demanded an apology.
But Mr Biden pushed back while attending fundraisers in the Washington DC suburbs on Wednesday night.
“There’s not a racist bone in my body,” he told reporters on the campaign trail. “I’ve been involved in civil rights my whole career.”
Mr Biden said he had “had to put up with” the segregationists, but that moderate Democrats “were able to beat them on everything they stood for”.
He added: “We, in fact, detested what they stood for in terms of segregation and all the rest.”
Biden refuses to apologise for working with racist senators