WASHINGTON — Senate Majority Leader Mitch McConnell set a crucial threshold vote for Friday on Brett Kavanaugh’s tottering Supreme Court nomination, moving his polarized chamber toward a potential confirmation roll call over the weekend that would determine which party wins an election-season battle royale that has consumed the nation.

McConnell, R-Ky., touched off the process late Wednesday and announced that sometime during the evening, the FBI would deliver to an anxious Senate the potentially fateful document on claims that Kavanaugh sexually abused women. With Republicans clinging to a razor-thin 51-49 majority and five senators — including three Republicans — still vacillating, the conservative jurist’s prospects of Senate confirmation remained murky and highly dependent on the file’s contents, which are supposed to be kept secret.

The report was arriving at a Capitol palpably tense over the political stakes of the nomination fight and from aggressive anti-Kavanaugh protesters who have rattled and reportedly harassed senators. Feeding the anxiety was an unusually beefy presence of the U.S. Capitol Police, who were keeping demonstrators and frequently reporters at arms length by forming wedges around lawmakers walking through corridors.

Amid complaints that some lawmakers were being confronted outside their homes, McConnell claimed on the Senate floor that the protesters were “part of the organized effort” to derail Kavanaugh’s nomination.

“There is no chance in the world that they’re going to scare us out of doing our duty,” he said.

Adding to the uncertainty, the three undecided GOP senators who could decide Kavanaugh’s fate rebuked President Donald Trump for mocking one accuser, Christine Blasey Ford, by mimicking her responses to questions at last week’s dramatic Senate Judiciary Committee hearing.

“I would tell him, knock it off. You’re not helping,” Trump ally Sen. Lindsey Graham, R-S.C., said of Trump’s Tuesday night tirade.

Senate Minority Leader Chuck Schumer, D-N.Y., said Trump’s insults marked a “new low.”

Barring leaks, it was unclear how much of the FBI report, if any, would be made public. While senators from both sides have expressed support for revealing at least parts of the findings, FBI background checks on nominees are supposed to remain confidential.

Underscoring rising tensions, Democrats suggested that previous FBI background checks of Kavanaugh may have unearthed misconduct by the nominee.

Democrats wrote to Senate Judiciary Committee Chairman Chuck Grassley, R-Iowa, challenging a Tuesday tweet by GOP aides saying prior investigations never found “a whiff of ANY issue — at all — related in any way to inappropriate sexual behavior or alcohol abuse.” Democrats wrote that the GOP tweet contained information that is “not accurate.”

Committee Republicans tweeted in response that their prior tweet was “completely truthful” and accused Democrats of “false smears.”

Sen. Susan Collins, R-Maine, told reporters that Trump’s lampooning of Ford at a Tuesday night Mississippi campaign rally was “just plain wrong.” Sen. Lisa Murkowski, R-Alaska, called it “wholly inappropriate and in my view unacceptable,” and Sen. Jeff Flake, R-Ariz., said on NBC’s “Today” show that the remarks were “kind of appalling.”

Those senators, along with Democrats Heidi Heitkamp of North Dakota and Joe Manchin of West Virginia, have yet to declare how they will vote.

“All of us need to keep in mind there’s a few people that are on the fence right now. And right now, that’s sort of where our focus needs to be,” said Sen. Bob Corker of Tennessee, who has traded barbs with Trump and will retire at year’s end.

Trump drew laughs Tuesday with his rendition of how Ford answered questions at last week’s hearing. “I had one beer — that’s the only thing I remember,” he stated inaccurately.

As he flew aboard Air Force One to the Mississippi rally, Trump was enraged by New York Times articles about Kavanaugh’s high school and college years and alleging tax avoidance efforts by the president and his family, according to a person familiar with the situation who spoke on the condition of anonymity.

White House counselor Kellyanne Conway on Wednesday echoed the president’s newly aggressive approach. She said Ford has “been treated like a Fabergé egg by all of us, beginning with me and the president,” and said Trump was merely “pointing out factual inconsistencies.”

The California psychology professor has testified that a drunken Kavanaugh sexually abused her in a locked room at a high school party in the 1980s and has said she believed he was trying to rape her. Kavanaugh has denied her assertions and those of two other women, who have accused him of other instances of sexual misconduct in the 1980s.

Ford’s attorney complained that the FBI has not contacted her for this week’s interviews. Democrats argued that the investigation has been insufficient, lacking interviews with her, with Kavanaugh and others who his accusers have said could know about the alleged incidents.

Lawmakers were making plans to begin reading the FBI report early Thursday, with senators and a small number of top aides permitted to view it in a secure room in the Capitol complex. Republicans have said they are working under an agreement governing background checks dating from the Obama administration, under which investigations are confidential and closely held.

Corker and Sen. Mike Rounds, R-S.D., said senators were expecting the document to contain reports that FBI agents compile on their interviews with subjects, perhaps accompanied by a cover letter. Background checks do not traditionally contain investigators’ conclusions about who they believe is credible.

Washington has been awaiting completion of the investigation since last week, when Flake, Collins and Murkowski pressured a reluctant Trump and GOP leaders to order the FBI to renew its background check of the 53-year-old Kavanaugh.

The FBI interviewed several people, including three who Ford has said attended a 1982 high school gathering in suburban Maryland where she says Kavanaugh’s attack occurred, plus another Kavanaugh friend. The agency has also spoken to a second woman, Deborah Ramirez, who has claimed Kavanaugh exposed himself to her at a Yale party when both were freshmen.

In an interview, No. 2 Senate Democratic leader Richard Durbin of Illinois said McConnell was “hell-bent on getting this done” this week.

Democrats also demanded that the FBI privately brief the Senate about the investigation before the chamber votes. McConnell rejected that request in a letter Wednesday to Schumer, saying Democrats would use it to delay Kavanaugh’s confirmation.

Associated Press writers Eric Tucker, Michael Balsamo, Catherine Lucey, Zeke Miller, Padmananda Rama, Matthew Daly, Mary Clare Jalonick and Kevin Freking contributed.

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