— 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, 95 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 with most, if not all, of the 51-senator GOP conference is expected to file into the room at 10 a.m.

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.

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.)

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.

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.