Booker acknowledged that he would "knowingly violating the rules."

Booker questioned Kavanaugh on Wednesday night about his stances on racial inequality, referring to emails from his time as a White House counsel for President George W. Bush. But, Republicans later pointed out, one of the emails he was referring to was labeled as "committee confidential."

Booker's threat immediately started a rhetorical firestorm among Judiciary Committee members.

Grassley, growing testy, interrupted Booker to ask: "How many times you going to tell us that?"

Democrats lamented that some documents were committee confidential, and Republicans warned that Booker would be breaking Senate rules.

"Running for president is no excuse for violating the rules of the Senate," Sen. John Cornyn John CornynThe Hill's Campaign Report: GOP set to ask SCOTUS to limit mail-in voting Liberal super PAC launches ads targeting vulnerable GOP senators over SCOTUS fight Senate GOP faces pivotal moment on pick for Supreme Court MORE (R-Texas) said to Booker. "I'd encourage our colleagues to avoid the temptation to either violate the Senate rules or to treat the witness unfairly."

Cornyn added that: "This is no different from the senator deciding to release classified information. ... That is irresponsible and outrageous."

Tens of thousands of documents have been given to the committee under the label of committee confidential.

But one by one, Democrats on the committee argued that the process wasn't fair. Democrats have taken issue with Bill Burck, Bush's lawyer, being able to sort through the documents. Burck is a former GOP staffer and colleague of Kavanaugh's.

"I have not made a big fight about this ... but again, lest silence imply consent, I think that rule is as ineffectual as if the chair had unilaterally repealed the law of gravity," Sen. Sheldon Whitehouse Sheldon WhitehouseHillicon Valley: Murky TikTok deal raises questions about China's role | Twitter investigating automated image previews over apparent algorithmic bias | House approves bill making hacking federal voting systems a crime House approves legislation making hacking voting systems a federal crime LWCF modernization: Restoring the promise MORE (D-R.I.) said. "It simply isn't so. I haven't agreed to this rule. I haven't voted on this rule."

Updated at 10:26 a.m.