A day into perhaps the biggest controversy facing Joe Biden since he declared his candidacy for the White House two months ago, it appears the front-runner in the race for the Democratic nomination is sticking to his guns.

Following a firestorm over comments earlier this week highlighting his ability decades ago to work with two segregationist southern senators to “get things done,” Biden's campaign is defending the comments while the candidate himself rebuffs calls for his apology -- and has fired back at his critics.

BIDEN SAYS BOOKER SHOULD APOLOGIZE

“Apologize for what?” Biden told reporters Wednesday night when asked about the criticism over his remarks. “Not a racist bone in my body. I've been involved in civil rights my whole career. Period. Period. Period.”

While none of his critics – including some of his top rivals for the nomination – are questioning Biden’s decades-long efforts to battle racism and strengthen civil rights, they are questioning whether the 76-year-old candidate is in tune with the Democratic Party of 2019. And the big question on the minds of many – will this unforced error put a dent in Biden’s aura of electability, which is a major factor in his current standing far ahead of the rest of the historically large field of some two-dozen Democratic White House hopefuls.

“I understand and respect that the [former] vice president was trying to refer to a period of civility when you disagree with someone – even a staunch segregationist,” said former Democratic National Committee chairwoman Donna Brazile, who as Al Gore’s campaign manager in the 2000 election became the first black person to steer a major political party’s presidential campaign.

“But I do believe the remarks were quite offensive,” Brazile, a Fox News contributor, told Fox News Radio.

Biden brought up the names of Sens. James Eastland of Mississippi and Herman Talmadge of Georgia while speaking at a fundraiser Tuesday in New York City. Eastland and Talmadge, two senior members in the Senate when Biden arrived in the chamber in 1973, were firmly opposed to desegregation efforts.

“I was in a caucus with James O. Eastland,” the 76-year old Biden said as he briefly imitated the late senator’s southern drawl. “He never called me boy. He always called me son.”

And he called long-deceased Talmadge “one of the meanest guys I ever knew.”

But discussing the “civility” in the Senate during the 1970s, according to the pool report, Biden said: “Well guess what? At least there was some civility. We got things done. We didn’t agree on much of anything. We got things done. We got it finished. But today, you look at the other side and you’re the enemy. Not the opposition, the enemy. We don't talk to each other anymore.”

The comments were part of Biden’s repeated warnings against Democrats who feel it’s not worth trying to find compromise with Republicans on the numerous divisive issues that have brought Washington to a standstill. Biden’s message of bipartisanship has been derided by some of his rivals for the Democratic nomination.

Biden’s comments came under attack on Wednesday by a number of his 2020 rivals, including Sens. Cory Booker of New Jersey and Kamala Harris of California – who are black – and New York City Mayor Bill de Blasio, who’s married to an African-American woman and has an interracial family.

Harris said on Wednesday that “if those men (Eastland and Talmadge) had their way, I wouldn't' be in the United States Senate…right now."

And on Thursday, she told Fox News that Biden’s comments were “misplaced and frankly misinformed.” She said she might speak to Biden about them.

Booker emphasized he was “disappointed” Biden had yet to issue an “immediate apology.”

“Vice President Biden’s relationships with proud segregationists are not the model for how we make America a safer and more inclusive place for black people, and for everyone,” Booker said. “You don’t joke about calling black men ‘boys.’ Men like James O. Eastland used words like that, and the racist policies that accompanied them, to perpetuate white supremacy and strip black Americans of our very humanity.”

Hours later, Biden returned fire, saying “Cory should apologize. He knows better.”

And he defended his Senate record as he took aim at Eastland’s rabid segregationist views.

“I could not have disagreed with Jim Eastland more, he was a segregationist. I ran for the United States Senate because I disagreed with the views of the segregationists in the Senate at the time. ... As I led the judiciary committee I was able to pass the Voting Rights Act while I was a young senator when he was the chairman, and he voted against it and we beat him in the Voting Rights Act," he said.

And he pointed to the late Sen. Ted Kennedy of Massachusetts, noting “he’s the guy who got me on the judiciary committee ... and we had to put up with the likes of like Jim Eastland and Hermy Talmadge and all those segregationists and all of that. And the fact of the matter is that we were able to do it because we were able to win-- we were able to beat them on everything they stood for.”

Biden’s response didn’t sit well with Booker.

“I was surprised he didn't apologize,” Booker said during a live interview on CNN Wednesday night.

“Vice President Biden shouldn't need this lesson and at a time when we have from the highest office in the land divisiveness, racial hatred and bigotry being spewed he should have the sensitivity to know that this is a time I need to be an ally, I need to be a healer, I need not engage in usage of words that will harm folks. And so, this is deeply disappointing,” Booker emphasized.

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But Symone Sanders, one of the most prominent black senior advisers on the Biden campaign, pushed back at the criticism aimed at her boss.

“I am all here for VALID CRITICISM, but suggesting that Joe Biden - the man who literally ran for office against an incumbent at 29 because of the civil rights movement, the man who was at the forefront of marriage equality before it was politically popular, the man who served as President Obama's VP, the man who literally launched his 2020 campaign calling out Nazis in Charlottesville along with Trump's equivalency - suggesting he is actively praising a segregationist is just a bad take and a willfully disingenuous act,” Sanders wrote on Twitter.

That said, Biden is still facing questions on why he chose to invoke his working relationship with two avowed segregationists – especially on the eve of Juneteenth, an American holiday that commemorates the June 19, 1865, announcement of the abolition of slavery in Texas and the broader emancipation of those held in slavery during the Confederacy.

“I would have preferred the vice president use other examples of working with people like Sen. John McCain. There’s so many people you could name,” Brazile argued, as she noted Biden’s decades-long bipartisan efforts first as a senator and later as vice president.

The controversy comes just a week before the first round of Democratic presidential primary debates – where Biden will face off on the same stage at the same time with many of his nomination rivals.

While critical, Brazile would not write off Biden due to this latest controversy.

“Joe Biden’s a well-known quantity, not only within the Democratic Party but the country. While this mistake might cost him some support, I still believe the vice president has a strong record on civil rights,” she noted.

Fox News' Peter Doocy contributed to this report.