Transcript for Firestorm as FBI investigation on Kavanaugh concludes
And we begin tonight with the supreme court showdown. That FBI investigation into allegations against judge Brett Kavanaugh is now finished, under lock and key. Senators timing into a secure room, beginning first thing this morning, to read it. And the reaction is pouring in tonight. Protesters marching in Washington from the supreme court to capitol hill. Hundreds of arrests tonight. Republican leaders saying they are satisfied with the FBI report into Kavanaugh, and Democrats tonight calling it a sham. Arguing only nine witnesses were interviewed, Dr. Christine blasey Ford nor Kavanaugh were among them. And the vote now comes down to just a handful of senators. Here's what they said so far. Republicans Susan Collins and Jeff flake spoke favorably about the report today. Lisa murkowski undecided tonight. Joe Manchin late today said he hasn't made up his mind. And snort Heidi Heitkamp revealing in a dramatic moment why she will vote no, even if she pays for it with her job. ABC's Mary Bruce chasing down those senators, what they're saying tonight about Brett Kavanaugh's future. Reporter: With the future of the supreme court hanging in the balance, hundreds of protesters made a final appeal on the streets of Washington. And in the halls of congress. The FBI report that could decide judge Kavanaugh's fate arrived on capitol hill at 2:30 A.M. Kept under lock and key in this secure room. Norring coming behind you. Reporter: This morning, one by one, senators trickle in. I didn't see it yet. Reporter: Republicans getting the first look. Among them, those key undecided votes, like Maine Republican Susan Collins. Good morning, senator. Good morning. Reporter: Behind these doors, just a single copy of the report. 46 pages of summaries from nine interviews with witnesses regarding judge Kavanaugh's alleged sexual misconduct. Leaving the room, two of those undecided senators seem satisfied with what they've seen. Collins tells reporters, "It appears to be a very thorough investigation." And Republican Jeff flake, he demanded the FBI investigate after he was confronted by two women. Look at me when I'm talking to you. You're telling me that my assault doesn't matter. That what happened to me doesn't matter and that you're going to let people who do these things into power. That's what you're telling me when you vote for him. Reporter: Today, flake sounding positive after seeing the report. I was a yes before this, and now, we're in the process of reviewing it, but thus far, we've seen no new credible corroboration. No new corroboration at all. Reporter: Another key holdout, Republican Lisa murkowski. Her decision still unknown. Senator, have you read the report yet? No, I'm going there now. Reporter: Last week, she told "The New York Times," "It's not about whether or not judge Kavanaugh is qualified. It is about whether or not a woman who has been a victim at some point in her life is to be believed." Also undecided, Democrat Joe Manchin of West Virginia. Late today, another critical vote, Heidi Heidkamp of North Dakota, tells our Fargo station WDAY news that she's voting no on Kavanaugh. For a Democrat up for reelection in a state president trump won by 36 points, it's an emotional decision. If this were a political decision for me, I certainly would be deciding this the other way. But you know, there's an old saying, "History will judge you, but most importantly, you'll judge yourself." And that's really what I'm saying. I can't get up in the morning and look at the life experience that I've had and say yes to judge Kavanaugh. Reporter: Today in the capitol, you could feel the tension. You are too committed to getting an abuser on the supreme court to even have a conversation and listen. If you gave him a polygraph, it would all be over, senator graham. Reporter: Tonight, Democrats calling the FBI investigation a sham. The bureau did not interview either judge Kavanaugh or Christine blasey Ford. Democrats agreed that the investigation's scope should be limited. We do not agree that the white house should tie the FBI's hands. Reporter: But Republican leaders say the investigation was credible and thorough and backs up the judge's story. They just about destroyed a good person to be on the supreme court. Reporter: Top Republicans now eager to move on. Enough. Enough already. Let's vote. Gets go live to Mary Bruce on the hill tonight. And that first crucial vote is expected in the senate tomorrow. Tell us how this works. And tonight, as you just reported, four of those five key senators have not revealed how they'll vote? Reporter: Well, David, we saw senators like Susan Collins come out and call this a thorough report, but she was just spotted leaving that secure room again, taking another close look, not just at this report, but also reading through transcripts of calls that came into the FBI tip line. But David, these undecided senators don't have a lot of time left to make up their mind. The senate is expected to vote to end debate on Kavanaugh's nomination tomorrow morning, setting up a final vote for Saturday afternoon. All right, if and when that happens, we'll carry it live with you on the air with us. Mary, thank you.
This transcript has been automatically generated and may not be 100% accurate.