"After reviewing his record and giving careful consideration to his answers during the hearing, I am not confident in Senator Sessions' ability to be a defender of the rights of all Americans, or to serve as an independent check on the incoming administration," the New York Democrat said in a statement. "I am also deeply concerned by his views on immigration, which I saw firsthand during the push for comprehensive immigration reform. For those reasons, I will oppose his nomination to serve as the next attorney general."
Schumer said the next attorney general must have a proven track record in fighting for the rights of all Americans.
"The attorney general must wake up every single day ensuring the rights of all Americans: immigrants, minorities, young and old, gay and straight, disabled and not are protected," he said. "Every right -- freedom of speech, freedom of religion, the freedom to vote, or any other enshrined in our Constitution or the law -- must be protected for every American."
Multiple civil rights groups, along with Democratic lawmakers, have expressed concern about Sessions' ability to represent historically disenfranchised groups given his past statements on the Voting Rights Act, the NAACP and allegations of racist language, which he has denied.
"Senator Sessions has failed to convince me that he will be a champion of constitutional rights: voting rights, women's health care and privacy rights, and anti-discrimination protections. Rather, he has demonstrated hostility and antipathy -- even downright opposition -- to these bedrock Constitutional principles," Sen. Richard Blumenthal, D-Connecticut, said in a statement Thursday announcing his opposition to Sessions.
Sen. Cory Booker -- who, in an unprecedented move for a sitting senator, testified against Sessions on Wednesday -- told CNN's Manu Raju Wednesday that his opposition to Sessions is due to the Alabama senator's criticism of the Justice Department's handling of issues such as police accountability, violence against women and voter rights.
"Jeff Sessions is out of line even with the Republican caucus," the New Jersey Democrat said. "While everybody, from (Senate Judiciary Committee) Chairman (Chuck) Grassley to Ted Cruz, Mike Lee, are all working together on issues around criminal justice reform, this is somebody who's criticized those very reforms."
Civil rights icon and Georgia Rep. John Lewis, who also testified against Sessions on Wednesday, called into question his commitment to being an advocate for Americans who have experienced discrimination.
"We need someone who is going to stand up, speak up and speak out for the people who need help, for the people who have been discriminated against," said Lewis, who marched for voting rights during the Civil Rights Movement.
West Virginia Democratic Sen. Joe Manchin, however -- who is facing a tough re-election fight in 2018 and vowed to back Sessions on the day he was nominated by President-elect Donald Trump to be attorney general -- reiterated his support Thursday, telling Fox News, "I can only say how I know the person, and I'm voting for the person I know."