Thousands of liberal protesters, fired up by Massachusetts Democratic Sen. Elizabeth Warren, marched up Capitol Hill on Thursday to protest Brett Kavanaugh’s nomination to the Supreme Court and put pressure on the handful of undecided senators who will determine whether Kavanaugh gets confirmed in the coming days.

By Thursday afternoon, Capitol Police began arresting hundreds of protesters inside the Hart Senate Office Building who raised their fists and loudly started chanting “Kavanaugh has got to go.” Arrests were made after protesters began sitting down in the building's atrium, refusing to cooperate with law enforcement.

In all, some 302 protesters were arrested and charged with unlawfully demonstrating in Senate office buildings Thursday, police said.

During the rallies and marches, protesters made it clear they were mad that Kavanaugh – who has denied allegations of past sexual assault – might be confirmed as early as this week.

“I am angry on behalf of women who have been told to sit down and shut up one time too many,” Warren, a possible 2020 Democratic presidential candidate, told the crowd.

Midday Thursday, demonstrators congregated at the Barrett Prettyman Courthouse in Washington, where Kavanaugh currently works as a United States Circuit Judge.

They then marched through the National Mall to the Supreme Court, where they shut down the street in front of the court and rallied some more. Speakers called out Republican senators Lisa Murkowski of Alaska, Jeff Flake of Arizona and Susan Collins of Maine.

“Senator Murkowski, do you believe us?” a female speaker from Alaska said on the steps of the Supreme Court. “You better believe us. You better believe survivors.”

Protesters waved signs that said, “Believe Survivors” and “Kava Nope.” Another read, “Susan Collins: Don’t betray women. Vote No.”

Some protesters may have been encouraged to attend the rally after the Party Majority PAC, a sponsor of the protest, listed the names of numerous supportive celebrities, including Alicia Keys, Eva Longoria, Whoopi Goldberg and Lena Dunham on its flier. Some news stories ahead of the event said they would be there, though none of those listed celebrities showed up.

Warren, who has acknowledged she is thinking of running for president in 2020 as a Democrat, was the biggest name to appear. Others who spoke included Linda Sarsour, the pro-Palestinian activist who helped lead the recent Women's March in Washington.

“I watched that hearing last Thursday, and I believe Dr. Ford,” Warren said, referencing Kavanaugh accuser Christine Blasey Ford. “I watched that hearing last Thursday, and Brett Kavanaugh is disqualified.”

Warren also took aim at the Republican men on the Senate Judiciary Committee.

“I watched 11 men -- powerful men -- try to help another powerful man make it to another powerful position,” the Democratic senator said. “This is about hijacking our Democracy.”

At one point during the march, protesters referenced the woman who accused Supreme Court Justice Clarence Thomas of misconduct during his 1991 confirmation hearings: “We believe Christine Ford. We believe Anita Hill,” they said.

The protests came the same day senators were able to read the FBI report on its investigation into Ford’s allegations against Kavanaugh.

Republicans said the report was thorough and showed that the FBI could not corroborate any of the allegations against Kavanaugh.

“The whole report, you can stand on it and paint the ceiling,” said Sen. John Kennedy, R-La.

“I learned nothing I didn’t already know,” said Lindsey Graham, R-S.C., who plans to vote for Kavanaugh.

Democrats, including those who have long said they planned to vote against Kavanaugh, said they weren’t satisfied.

“There is much in there that raises more questions,” said Cory Booker, D-N.J.

The prospects for Kavanaugh's confirmation now rest on four swing senators.

North Dakota Democratic Sen. Heidi Heitkamp, after staying on the fence for weeks, announced Thursday she will vote against Kavanaugh, citing in part his conduct at last week's fiery Hill hearing.

But at least two Republican swing senators indicated they were satisfied with the FBI’s investigation.

Collins, who has stayed mum on her Kavanaugh stance, said Thursday that the bureau’s supplemental background probe “appears to be a very thorough investigation.”

And Flake, who originally requested the FBI re-open its investigation into the claims leveled against Kavanaugh by Ford, said no “new corroborative information came out” of the report.

The other two big undecideds are Murkowski and Democratic Sen. Joe Manchin, of West Virginia.

Murkowski said Thursday she has made "no decision" on Kavanaugh's fate. Manchin's stance is not yet clear.

Fox News’ Mike Emanuel, Chad Pergram, NuNu Japardize, David Sweet and Brooke Singman contributed to this report.