WASHINGTON — Black lawmakers said Wednesday that Senator Jeff Sessions at times has shown hostility toward civil rights, making him unfit to be attorney general, as a 1986 letter from the widow of Martin Luther King Jr. surfaced strongly expressing opposition to the Alabama senator.

In the second day of confirmation hearings, New Jersey Democratic Senator Cory Booker, Sessions’ colleague, and Representative John Lewis, a Georgia Democrat who was beaten when he marched for civil rights in the 1960s, warned that Sessions could move the country backward if confirmed as Donald Trump’s top law enforcement official.

Booker said the ‘‘arc of the universe does not just naturally curve toward justice, we must bend it,’’ and the country needs an attorney general who is determined to bend it.

‘‘Senator Sessions’ record does not speak to that desire, intention, or will,’’ Booker said, noting his opposition to overhauling the criminal justice system and his positions on other issues affecting minority groups.

Lewis told the Senate Judiciary Committee that the country needs ‘‘someone who’s going to stand up, speak up, and speak out for the people that need help, the people who have been discriminated against.’’

And Representative Cedric Richmond, a Louisiana Democrat who is chairman of the Congressional Black Caucus, urged senators to reject Sessions’ eventual nomination because he has ‘‘advanced an agenda that will do great harm’’ to African-Americans.

The lawmakers’ criticism echoed Cornell Brooks, the head of the NAACP, who told the panel earlier in the day that the organization ‘‘firmly believes’’ Sessions is unfit to serve.

The Alabama Republican was rejected by the Judiciary panel in 1986 for a federal judgeship amid accusations that he had called a black attorney ‘‘boy’’ — which he denied — and the NAACP and ACLU ‘‘un-American.’’

Sessions on Tuesday called those accusations ‘‘damnably false’’ and said he is ‘‘totally committed to maintaining the freedom and equality that this country has to provide to every citizen.’’

The lawmakers’ testimony brought two days of confirmation hearings for Sessions to a close. He has solid support from the Senate’s Republican majority and from some Democrats in conservative-leaning states, and is expected to easily win confirmation. But Democrats are using the hearings to try to show that Sessions — and Trump’s administration — won’t be committed to civil rights, a chief priority of the Justice Department during the Obama administration.

On Tuesday, the NAACP released a 1986 letter from Coretta Scott King, widow of the civil rights leader, in which she said that Sessions’ actions as a federal prosecutor were ‘‘reprehensible’’ and that he used his office ‘‘in a shabby attempt to intimidate and frighten elderly black voters.’’

‘‘Mr. Sessions has used the awesome power of his office to chill the free exercise of the vote by black citizens in the district he now seeks to serve as a federal judge,’’ Mrs. King wrote. Mrs. King died in 2006.

Richmond complained during his testimony that putting the all-black panel at the end of the hearings was akin to being made to go to the ‘‘back of the bus,’’ a reference to 1960s segregation laws. During his testimony, many members of the Congressional Black Caucus sat in the audience.

Not everyone on the panel criticized Sessions. Three men who had worked with Sessions in Alabama and Washington, all black, testified in support.

Jesse Seroyer, a former US marshal for the Middle District of Alabama, said Sessions is a ‘‘good honest person who is going to give all he has to make sure everyone is treated fairly under the law.’’

Earlier in the day, former attorney general Michael Mukasey also came to Sessions’ defense at the hearing. He wrote in his testimony that ‘‘of all the insidious practices that have crept into our politics in recent times, I know of none more insidious than casual and unjustified accusations of racism, smears that once leveled are difficult to wipe clean.’’