Senate Minority Leader Chuck Schumer (D-N.Y.) will not support Sen. Jeff Sessions (R-Ala.) for attorney general, he announced on Thursday.

Other Democrats in the Senate have spoken out against Sessions, including Cory Booker (D-N.J.), but Schumer is the highest ranking one to do so. Schumer said in a statement:

“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. 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 further explained his logic in a series of tweets:

The Attorney General has a sacred obligation to enforce our laws & uphold the constitution. — Chuck Schumer (@SenSchumer) January 12, 2017

The AG ensures that POTUS & the Admin's policies adhere to American values& ideals & is a check to ensure the President is not above the law — Chuck Schumer (@SenSchumer) January 12, 2017

I am not confident in Sen Sessions' ability to defend the rights of all Americans, or to serve as indep. check on the next administration. — Chuck Schumer (@SenSchumer) January 12, 2017

Also deeply concerned by Sen Sessions' views on immigration, which I saw firsthand during the push for comprehensive immigration reform. — Chuck Schumer (@SenSchumer) January 12, 2017

Sen. Richard Blumenthal (D-Conn.) also came out against the nomination Thursday.

“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,” he said in a statement. “Rather, he has demonstrated hostility and antipathy ― even downright opposition ― to these bedrock Constitutional principles.”

Democrats have been quick to criticize Sessions’ record on civil rights, pointing out that he was rejected for a federal judgeship position in 1986 over allegations of prejudice against African-Americans. In particular, a coalition of black lawmakers said that the Alabama lawmaker’s opposition to the Voting Rights Act, immigration, and LGBTQ protections makes him unfit to be attorney general.

“Sen. Sessions has not demonstrated a commitment to a central requirement of the job ― to aggressively pursue the congressional mandate of civil rights, equal rights and justice for all,” Booker said. “In fact, at numerous times in his career, he has demonstrated a hostility toward these convictions.”

As no Republicans have said they will reject Sessions, it’s unlikely that Democrats’ efforts will affect his chances.

This article has been updated with comment from Sen. Richard Blumenthal.