WASHINGTON -- U.S. Sen. Cory Booker on Thursday released confidential documents about U.S. Supreme Court nominee Brett Kavanaugh, even though he could be expelled from the Senate for that action.

Booker, a New Jersey Democrat, was joined by U.S. Sen. Mazie Hirono, D-Hawaii, in releasing the documents that had been declared confidential by a veteran Republican lawyer.

"I come from a long line, as all of us do as Americans, understand what that kind of civil disobedience is and I understand the consequences," Booker said.

"This is about the closest I'll have in my life to an 'I am Spartacus' moment,'" he also said.

Booker referred to the documents Thursday when he asked Kavanaugh about an email that described preferences for minorities who faced discrimination as a "naked racial set-aside." The document had been declared confidential by a veteran Republican lawyer who has represented Trump administration officials.

These are the 4 documents marked committee confidential that I brought up in my questioning of Supreme Court nominee Brett Kavanaugh last night --> https://t.co/2RZkY2FS9a — Cory Booker (@CoryBooker) September 6, 2018

During the hearing on Thursday, Booker had said he would release the documents despite the consequences.

"The emails being withheld from the public have nothing to do with national security," Booker said.

Sen. @CoryBooker: "I'm knowingly violating the rules. Sen Cornyn has called me out for it. I'm saying right now that I'm releasing committee confidential documents."



Senator @JohnCornyn: "Running for president is no excuse for violating the rules of the Senate…" pic.twitter.com/A2pB19ENPP — CSPAN (@cspan) September 6, 2018

Senate Majority Whip John Cornyn, R-Texas, a member of the Senate GOP leadership that disregarded legislative norms and refused to consider President Barack Obama's nomination of Judge Merrick Garland for the Supreme Court, called Booker's threat "irresponsible and outrageous."

"No senator deserves to sit on this committee or serve in the Senate in my view if they decide to be a law unto themselves," Cornyn said.

Traditionally, the National Archives would review Kavanaugh's papers from his time in the federal courts and his tenure in President George W. Bush's White House, a process that will take until the end of next month.

Instead, Senate Judiciary Committee Republicans, over Democratic objections, had Bush lawyer Bill Burck, a veteran Republican attorney who also has represented Trump administration officials go through the papers and decide which ones the panel can see, and which of those can be made public.

Papers released to the members of the committee but not allowed to be made public are considered "committee confidential."

Booker received support from his fellow Democrats.

.@maziehirono, your friends in the House are with you. The #KavanaughHearings are highly irregular. Thanks for standing up and speaking out. https://t.co/tj4GzWahMr — Rep. Donald Payne Jr (@RepDonaldPayne) September 6, 2018

Booker is mentioned as a potential Democratic presidential candidate, and Senate Republicans see his actions as a sign that he has national aspirations.

"I don't ever plan for running for president in 2020," said U.S. Sen. Thom Tillis, R-N.C.

Jonathan D. Salant may be reached at jsalant@njadvancemedia.com. Follow him on Twitter @JDSalant or on Facebook. Find NJ.com Politics on Facebook.