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Judge Brett Kavanaugh’s nomination to be the next Supreme Court justice will be decided Thursday.

All 100 senators will be able to review the supplemental background investigation throughout the day. A reminder that barring some dramatic disclosure in from that inquiry, 96 senators have already made up their minds. How the remaining groups sees the new background information – and how it factors into their decisions – will drive the day.

It all comes down to five senators – three Republicans and two Democrats – and what they see today behind closed doors. Here are the rules senators are following to review the documents.

The format

Judiciary Committee Republican staff got the first look at the FBI’s findings starting at 8 a.m. ET. At 9 a.m. ET, Democrats took over the room. Control of the room is scheduled to rotate, every other hour, for the rest of Thursday.

The staff that is cleared to review the material will provide briefings, likely to groups of senators, and the senators will be able to review the raw 302s themselves.

Sen. Ron Johnson, a Republican from Wisconsin, told reporters that staff from the office of Senate Judiciary Chairman Chuck Grassley are reading the report aloud to senators and then other interviews (that aren’t being read aloud) are being passed around for senators to look at.

There is only one copy, which is making things interesting.

“We are trying to get it all done efficiently,” Johnson said.

The rules

  • This FBI’s work is not public. It will likely never be public. There will be no summary. There will be no release.
  • There are 109 people who have clearance to access what was delivered to Capitol Hill at 2:30 Thursday morning – 100 senators, four majority committee staffers and four minority committee staffers, one committee clerk. That’s it.
  • There is a single copy of the FBI’s findings. It is currently in a vault, in a Sensitive Compartmented Information Facility – or SCIF, if you’d like to use the Washington short hand. It cannot leave the room.
  • Senators can’t bring their phones into the SCIF when they go to review the documents. If they take notes, the notes must be left in the room when the senator leaves.
  • Senators are not allowed to discuss or characterize in detail what they’ve read (though they most certainly will try.)

Inside the room

Johnson told reporters that in the SCIF, there are little stands with microphones, where the judiciary staff is “somewhat taking turns” briefing lawmakers from the FBI report.

“I’ve never seen anything like that before,” Johnson told reporters. “This is unusual circumstances calling for kind of (an) unusual process.”

Johnson said the staff will stay as long as people want to come read the report.

“There is discussion too. There are questions being answered,” Johnson said. “I personally find it to be a pretty good, pretty efficient process.”

What that means

The public is expected to only be able to gauge what’s in the FBI’s findings in two ways:

First: the topline characterizations of senators who read the documents. Reminder these senators have very specific motivations for how they characterize what they see, especially given it won’t be publicly released.

Second: By the votes on the Senate floor. If the undecided senators all get to “yes,” then they saw something that assuaged their concerns – or at least didn’t create any more.

Important point

This is, quite literally, how the process is designed to work, as guided by a bipartisan Judiciary Committee memorandum of understanding signed in 2009. Background investigations are not supposed to be made public – in fact, it’s against the law to do so. The limited number of people with access, the restrictions on public disclosure, even the number of copies provided, are all dictated by rules the committee agreed to nine years ago.

It’s worth noting – Republican senators discussed for days whether there was a way to make some form of the information public, either in summary form or some other mechanism. It was decided that given the rules in place, and the potential legal issues, it isn’t doable at this point.

What the White House is saying

The White House has explored ways to make some of the FBI report public, an official familiar with the deliberations says, but lawyers have determined it would be very difficult without violating the Privacy Act or the memorandum of understanding that dictates how the information is shared.

Officials feel if the report was made public it would prove the “no corroboration” line they and Senate Republicans have been projecting this morning. But as of Thursday morning, they believe there is very little they will be able to make public, or comment on specifically.

Separately, a senior White House official told CNN they won’t call for the release of the background investigation — and claims the Senate can’t release it either.

What Senate GOP leaders believe right now

Multiple senior GOP aides expressed confidence Wednesday night that Kavanaugh was on the path to confirmation – though all acknowledged Senate Majority Leader Mitch McConnell still hasn’t received any commitments or assurances from the undecided senators.

The expectation, aides say, is barring some significant new disclosure in the FBI inquiry, they’ll make it over the vote threshold to get Kavanaugh confirmed.

“We’ve made sure they got what they needed,” one of the aides said. “Now we move forward.”

The week-long delay is almost over. The FBI supplemental background check is officially on Capitol Hill. The first vote is scheduled for Friday. This is moving, one way or another.

CNN’s Lauren Fox, Ted Barrett, Sarah Westwood and Kevin Liptak contributed to this report.