(CNN) In Washington, the next attorney general insisted at his confirmation hearing that he is not a racist. And in Chicago, the nation's first black president offered a fiery farewell -- and a warning.

Speaking to emotional supporters in Chicago, President Barack Obama described racial animus in America, persistent and pervasive, as a "threat to our democracy."

"After my election," he said, "there was talk of a post-racial America. Such a vision, however well-intended, was never realistic. Race remains a potent and often divisive force in our society."

The weight and implacability of those divisions were on display back in Washington, where Alabama Sen. Jeff Sessions, denied a federal judgeship more than 30 years ago amid charges he called a black colleague "boy" and hinted at past sympathy for the Ku Klux Klan, sought to disarm critics on Capitol Hill.

Sessions will face criticism during a second day of scrutiny, including from Sen. Cory Booker, who is taking the unprecedented step of testifying against his colleague.

As Obama touched down in Chicago, where he had been working as a community organizer the last time Sessions faced the Senate Judiciary Committee, the Alabama senator in his opening remarks dismissed the allegations that scuttled his 1986 nomination as "damnably false."

"I abhor the Klan and what it represents, and its hateful ideology," Sessions said in his opening remarks Tuesday, touting his role in the investigation, conviction and eventual execution of a KKK member who took part in the 1981 lynching of a 19-year-old black man in Mobile, Alabama.

As Sessions looked back, seeking to recast a lifetime on the fault lines of the American racial divide, Obama offered what administration officials had promised would be a "forward-looking" vision for Americans, in particular the loyal liberals who supported him and, in 2016, Hillary Clinton.

"If we're going to be serious about race, we must uphold laws against discrimination -- in hiring, in housing, in education and the criminal justice system," Obama said to roars in McCormick Place. "That's what our Constitution and highest ideals require. But laws alone won't be enough. Hearts must change."

Back in Washington, Sessions had sought to soften his public image. He appeared at the outset with young grandchildren on his lap. Asked by the sympathetic Sen. Lindsey Graham how being accused of racism made him feel, Sessions cast his younger self as the naive victim of a ruthless smear campaign.

"When you have a Southern name, you come from South Alabama that sounds worse to some people," he said softly. "When I came up as a US attorney, I had no real support group. I did not prepare myself well in 1986 and there was an organized effort to caricature me as something that was not true. And, it was very painful. I didn't know how to response and didn't respond very well."

Sessions survived. He was rejected by the Senate then, but was elected to it later. For his years there, he seemed to enjoy an unlikely deference, and not only from Republicans. Apart from a few sharp exchanges with Minnesota Sen. Al Franken, who suggested the nominee had overstated and misled the public about his civil rights record, his colleagues pushed but never sought a knockout blow.

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Over the hours, Sessions hardened. Presented with evidence of compromising relationships with known bigots like anti-Muslim conspiracy theorist Frank Gaffney Jr., the senator pleaded ignorance. Later on in Tuesday's hearing he expressed skepticism over the use of federal consent decrees to address police abuses.

"These lawsuits undermine the respect for police officers and create an impression that the entire department is not doing their work consistent with fidelity to law and fairness," he said. "We need to be careful before we do that."

But even as the hearing oscillated between skeptical, if restrained, Democrats and approving Republicans, a Greek chorus of protesters and stood up at regular intervals to shout down the nominee.

Groups of demonstrators, many from Code Pink, chanted "No Trump, No KKK, no fascist USA," as security escorted them out. Another yelled, "Black lives matter" as activists nearby crowded inside Sessions' own office, demanding the senator withdraw his name.

The first from the upper chamber to back President-elect Donald Trump during the 2016 campaign, Sessions' record as a lawmaker and prosecutor has come under intense scrutiny by the press and political opponents. His path to becoming the nation's most powerful law enforcement officer has been sharply contested by a range of progressive groups, ranging from grassroots activists to established organizations like the NAACP and ACLU, whose national legal director, David Cole, will testify during the second round of hearings on Wednesday.

Sessions' judgeship was sunk in part because he referred to those groups' work as potentially "un-American." On Tuesday he argued that the remark was made in an effort to aid and preserve the NAACP's "moral authority."

"My comment about the NAACP arose from a discussion I had where I expressed concern about their statements that were favoring, as I saw it, Sandinista efforts and communist guerrilla efforts in Central America," Sessions said.

"And so I said they could be perceived as 'un-American' and weaken their moral authority to achieve the great things they had been accomplishing in integration and moving forward for reconciliation throughout the country."