Sen. Cory Booker (D-N.J.) spoke at the confirmation hearing, Jan. 11, for attorney general nominee Jeff Sessions. (Reuters)

Later Wednesday, Sen. Cory Booker (D-N.J.) will become the first sitting senator to testify against a fellow senator’s nomination for a Cabinet post, when he makes the case against confirming Sen. Jeff Sessions (R-Ala.) as attorney general. On Tuesday evening, he told The Washington Post how he came to make the decision, which was swiftly criticized by Republicans as a way to grab the spotlight.

Why did you decide to do this?

So many of the issues that have been driving me since I was a city councilperson in Newark deal in areas of justice, equal opportunity, civil rights, LGBT rights. So many have to deal with this issue. I’m grateful for the senators that were able to ask thorough questions, but this is one of those times where on issues at the core of justice in America, issues that have been a strike point as we’ve seen over the last few years, issues at a time when America needs healing to address a lot of the things that are causing such rifts in our country, the most important law enforcement officer in the country, this is a position of profound importance on issues that go to the core of what we are as a country. To remain silent at this time, to me, is unacceptable. Even if it means breaking norms on issues of this kind of gravity, I could not have sat well with my own self to remain silent on issues that are the core of our conceptions of justice.

The career of Jeff Sessions, President-elect Donald Trump's nominee for attorney general, has been shadowed by his prosecution of the "Marion Three." Sessions brought forth the voter fraud case as a U.S. attorney in 1985, and his critics alleged the charges to be racially motivated. (Dalton Bennett/The Washington Post)

Are you concerned about decorum?

I absolutely do worry about that, but you have to understand, when I go home, I go home to an inner-city community where the ravages of the lot of the challenges – equal justice under the law, the challenges with the criminal justice system, the challenges that core people face in getting a fair shake — where a lot of these issues have been a part of my life for a long time. I know that a lot of the folks who — when it comes to the justice system in America, people feel voiceless or that their lives don’t matter. For m,e to be silent in this moment in history, would be unacceptable to them and is unacceptable to me.

What about your work with Sessions in the past, on honors for civil rights activists?

I don’t want to get ahead of myself, because I address this in my remarks. It actually — in fact, some of the things that helped compel me to testify in the first place have to do with the marchers at Selma. But please understand, and I’m going to be short here, because I don’t want to take away from my testimony tomorrow, but I am where I am today directly because of leaders in the legal community who felt it was their affirmative obligation to defend the civil rights of others. I don’t say that just as somebody who is a generation born after the civil rights movement — and we all stand on the shoulders of giants. But I am where I am today directly because of activists in Alabama.

How do you mean?

I’ll explain that [Wednesday]. Not just the activists in Alabama, but the legal professionals who really saw an urgency in fighting for the rights of all Americans. I am really proud to have worked with Jeff Sessions on awarding that medal to those marchers. I am really grateful for the collegial relationship that he and I have had, the frank conversation, the decorum with which he had greeted me and I hope that he thinks I have greeted him.

How has Sessions reacted to your decision?

I met with him [Monday] with staff there, and that feeling of goodwill was there and he knew I was going to testify. This is not in any way, to me, an undermining of that collegiality that has continued and, as a result of us talking yesterday, will continue. He expressed to me, as I expressed to him, that should he become the attorney general, we have to work together. I think that our paths — even though we disagreed a lot, our past pattern of working together despite our vast differences — he is a guy in an environment where we’ve had bipartisan progress on things like criminal-justice reform. He’s been one of the few senators fighting against what has been years of my work in cooperation with people like Mike Lee and Chairman [Charles] Grassley.

Our differences don’t undermine the places where we find commonality or the collegiality that we enjoy. I am a United States senator. He is up for the most important law enforcement position in the country. Just voting yay or nay on this is insufficient, given the grand import of that position. This is a time where I think that silence is not just unacceptable, but in many ways, if Jeff Sessions continues as a U.S. attorney general in doing things that undermine reform, that undermine civil rights, that undermine equality under the law, that undermine voting rights, that undermine the advancement of gays and lesbians in this country, that silence at this point in history, silence would be tantamount to complicity to things that I fear he would do in that office.

When did you decide to do this?

I released a statement immediately [after the nomination was announced]. I called him on his cellphone but didn’t have a connection and … I know Jeff Sessions well enough that on the issues that I’ve been dedicating my life to over the last few years, I know the stance that he’s taken, I know that he’s worked against many of the things that both Democrats and Republicans, Heritage Foundation, American Enterprise Institute, Koch Institute have been working together on. I knew what it would be if someone like that were to become the attorney general. This was literally moments after what I knew what was going to happen. I let him know my grave concerns. I released statements on social media. This was nothing that I think he had a realization to. Then I thought long and hard what I felt were my obligations in standing up and speaking out against his nomination. So, again, I felt that as a colleague, that I should sit face to face with him and we should have this discussion.

And what was that conversation like?

It was cordial and collegial as we have always been with each other. I have a great respect for him as a colleague. We have always been respectful to each other. I don’t see this in any way as contrary to the relationship we’ve had. This is a moment where I felt a moral obligation to speak out because I feel that silence in these moments in history are unacceptable.