Washington (CNN) The bitter Brett Kavanaugh's confirmation battle raged all over Capitol Hill on Thursday, even as his chances of reaching the Supreme Court appeared to improve after an FBI probe into allegations of sexual misconduct against him.

Angry protests by anti-Kavanaugh campaigners mixed with deep mistrust festering between Republican and Democratic senators offered a glimpse of the political discord that will be the left behind if Republicans succeed in the long quest to elevate him to the court in the next few days.

After a tense day on Capitol Hill, Kavanaugh's fate is not yet resolved, since three Republican swing senators who have been studying the FBI report have yet to indicate how they will vote, and Senate Majority Leader Mitch McConnell can afford to lose only one of his troops.

But Arizona Sen. Jeff Flake, who forced the supplemental FBI investigation following Christine Blasey Ford's emotional testimony against Kavanaugh last week in the Senate Judiciary Committee, said: "we've seen no additional corroborating information" to support the allegations.

Another crucial Republican, Sen. Susan Collins of Maine said the report appeared to be "a very thorough investigation" and returned several times to the secure room in the Capitol where staffers were reading the sole copy of the report aloud to senators.

"I'm not going to draw conclusions before I'm finished reading," Collins said.

A third key Republican vote, Sen. Lisa Murkowski of Alaska, made clear she wouldn't decide until she had studied all the evidence.

But even as his senators deliberated under extreme political pressure, McConnell pressed ahead with an aggressive effort to bring the drama to a successful close, ahead of a decisive procedural vote on Friday.

"What we know for sure is the FBI report did not corroborate any of the allegations against Judge Kavanaugh. And the second thing we know for sure is that there's no way anything we did would satisfy the Democrats," McConnell said.

Hundreds arrested

The final twists of the tumultuous Kavanaugh confirmation drama unfolded amid high tension.

Capitol Police arrested 302 protesters in the Hart Senate Office Building. Comedienne Amy Schumer was seen amongst those being detained. Earlier, at a rally in Washington anti-Kavanaugh demonstrators chanted: "Hey hey, ho ho, Kavanaugh has got to go"

Madison Thomas, a survivor of sexual assault and an organizer with the Women's March Youth Empower organization, said the confirmation battle had revealed the true motivation of America's elected representatives.

"What the hearings told me was that our country, our congressmen, value the reputation and the career aspirations of my male classmates, or men, of my assaulter, more than my bodily autonomy," Thomas said.

In another scene that has become typical in recent days, a group of protestors confronted Utah Republican Sen. Orrin Hatch in a corridor, and reacted furiously when he told them to "grow up."

As momentum appeared to be building for Kavanaugh, Ford's lawyers wrote to FBI Director Christopher Wray to complain that the bureau did not interview Ford or witnesses who had information on her allegations.

"The 'investigation' conducted over the past five days is a stain on the process, on the FBI and on our American ideal of justice," read the letter from attorneys Debra Katz, Lisa Banks and Michael Bromwich.

Democrats tried to counter Republican arguments that the FBI investigation, which will not be released to the public, contained nothing to corroborate Ford's allegations that she was assaulted by Kavanaugh when they were teenagers in the Washington DC suburbs in the early 1980s. Kavanaugh has denied the allegations.

"It looks to be a product of an incomplete investigation that was limited, perhaps by the White House," Sen. Dianne Feinstein, the top Democrat on the Judiciary Committee, told reporters.

Senate Minority Leader Chuck Schumer disputed the notion that the FBI had conducted a thorough investigation and demanded its details be made public.

"Why shouldn't all of America see the facts?" Schumer asked.

Politics of personal destruction

The level of animosity whipped up by the Kavanaugh confirmation process is startling and at odds with the normally courtly code of the Senate, and reflects the gaping cavern that has opened up in the nation over the issue.

"What I've been dealing with since July the 10th, the downhill slope that Schumer's put us on is really dealing with a demolition derby," said Senate Judiciary Chairman Chuck Grassley of Iowa.

"They just about destroyed a good person to be on the Supreme Court."

Hatch accused Democrats of trading in the "politics of baseless personal destruction."

New York Democratic Sen. Kirsten Gillibrand urged protestors to turn their fury over the confirmation saga into political energy.

"I'm leaving you with one final thought: November is coming. November is coming. November is coming," she said, referring to the mid-term elections in which both parties hope to leverage the Kavanaugh controversy to energize their voters.

Another Democrat, Sen. Heidi Heitkamp of North Dakota, one of two Democrats fighting for re-election in states where Trump won big in 2016, had been seen as a potential vote for Kavanaugh but announced Thursday she would oppose him. She cited concerns about his past conduct and his temperament following his fiery performance before the Judiciary Committee last week.

Another Democrat in a similarly tough political position, Sen. Joe Manchin of West Virginia, has yet to say how he will vote and plans to return to the secure room on Friday morning to finish his assessments.

"Heidi made her decision, I'll make mine," he said.

One source told CNN's Ariane de Vogue that the report sent to the Hill by the FBI includes 45 pages of interview summaries and 1,600 extra pages of information that the bureau sent up from their tip line.

For once, Trump, who was criticized by some Republicans on Wednesday for mocking Ford's testimony, did not rock the boat.

He told reporters: "I think he's doing very well. The Judge is doing well." The President's discipline will face more of a test later on Thursday when he holds a campaign rally in Minnesota.