New Jersey Sen. Cory Booker on Wednesday became the first sitting senator to formally testify against a sitting senator in a nomination hearing — against Jeff Sessions, President-elect Donald Trump’s nominee for attorney general.

Booker, who’s black and comes from a family that faced discrimination while trying to move to a white neighborhood decades ago, drew from his own life story, putting it in contrast to Sessions’s record on civil rights issues. “I am literally sitting here because of people — marchers in Alabama and volunteer lawyers in New Jersey — who saw it as their affirmative duty to pursue justice,” he said. “But the march for justice in our country still continues.”

“Sen. Sessions has not demonstrated a commitment to a central requisite of the job — to aggressively pursue the congressional mandate of civil rights, equal rights, and justice for all of our citizens,” Booker argued. “In fact, at numerous times in his career, he has demonstrated a hostility towards these convictions and has worked to frustrate attempts to advance these ideals.”

He added, “If confirmed, Sen. Sessions will be required to pursue justice for women, but his record indicates that he won’t. He will be expected to defend the equal rights of gay and lesbian and transgender Americans, but his record indicates that he won’t. He will be expected to defend voting rights, but his record indicates that he won’t. He will be expected to defend the rights of immigrants and affirm their human dignity, but the record indicates that he won’t.”

Booker has long presented himself as a bipartisan figure in the Senate, but he said he had to make an exception in this case. “I know it is exceptional for a senator to testify against another senator nominated for a Cabinet position,” Booker said. “But I believe, like perhaps all of my colleagues in the Senate, that in the choice between standing with Senate norms or standing up for what my conscience tells me is best for our country, I will always choose conscience and country.”

There may be a political motive here: Booker is often named a rising Democratic star who could run for president in the coming years. But as far as his claims, there is a lot of reason for civil rights advocates to find Sessions’s record deeply troubling.

The record is especially worrying given the position that Sessions has been nominated for. As head of the US Department of Justice, he will be charged with enforcing federal civil rights laws that protect minority groups and women from discrimination and hate crimes. Yet at multiple times in his career, Sessions has questioned whether these laws are necessary in the first place.

Sessions has a troubling record on civil rights

Sessions has been heavily criticized for opposing policies that would protect minority groups — typically by denying that these groups face any discrimination at all.

During discussion in 2009 about a new federal hate crimes law that would protect LGBTQ people and women, Sessions said, “Today, I'm not sure women or people with different sexual orientations face that kind of discrimination. I just don't see it.” FBI data, while imperfect, shows that LGBTQ people are more likely to be targets of hate crimes than other minority groups.

Sessions previously said that the Voting Rights Act, which allowed the federal government to oversee elections in states with histories of racism, is a “piece of intrusive legislation.” And when the US Supreme Court struck down parts of the law, Sessions argued that Shelby County, Alabama, where the Supreme Court challenge came from, “has never had a history of denying voters and certainly not now” — even though the county, like Alabama generally, has a long, long history of discrimination of all kinds.

Sessions has tried to rebuke some of the criticisms against him by arguing that as a federal prosecutor, he took charge in several civil rights cases. In a questionnaire filed to the Senate Judiciary Committee for his nomination, Sessions cited four civil rights cases as among the 10 most significant cases he took part in “personally.”

But civil rights lawyers who actually litigated these cases have disputed Sessions’s close involvement. As three civil rights lawyers wrote at the Washington Post, “We worked in the Justice Department’s Civil Rights Division, which brought those lawsuits; we handled three of the four ourselves. We can state categorically that Sessions had no substantive involvement in any of them. He did what any U.S. attorney would have had to do: He signed his name on the complaint, and we added his name on any motions or briefs. That’s it.”

Taken together, Sessions’s history has pushed civil rights advocates like the NAACP and ACLU to come out against his nomination for attorney general. After all, if he doesn’t believe discrimination exists, how can he be expected to prevent and stop it?