Brett M. Kavanaugh and his wife, Ashley Kavanaugh, arrive for a Senate Judiciary Committee hearing on Capitol Hill on Sept. 27, 2018. (Carolyn Kaster/AP)

Democrats and representatives for those who claimed to have been victimized by Brett M. Kavanaugh angrily denounced the FBI’s background check of Kavanaugh on Thursday, asserting that the bureau, shackled by the White House, did not pursue obvious leads that could have helped corroborate the allegations the Supreme Court nominee faced.

The FBI interviewed nine people in its week-long look at Kavanaugh, and the White House and Republicans seized on its findings to declare that the claims of sexual misconduct remained uncorroborated. Sen. Susan Collins (R-Maine), considered a critical swing vote on Kavanaugh’s nomination, said the probe seemed to be “a very thorough investigation.”

Democrats, though, disputed those characterizations, asserting that what was more important than what the bureau did not find was what its agents did not pursue.

Sen. Robert Menendez (D-N.J.), who has been repeatedly investigated by the FBI, called the bureau’s work on the Kavanaugh matter “a bulls--- investigation. The reality is that is not a full and thorough investigation. . . . You don’t get corroboration if you don’t talk to corroborating witnesses.”

Lawyers for two of Kavanaugh’s accusers said the FBI did not interview dozens of people whose information they provided and who would have supported their clients’ accounts.

“The ‘investigation’ conducted over the past five days is a stain on the process, on the FBI and on our American ideal of justice,” lawyers for Christine Blasey Ford, who claims Kavanaugh sexually assaulted her when both were in high school, wrote in a letter to FBI Director Christopher A. Wray.

An FBI spokeswoman declined to comment.

The FBI has spent most of the past two years at the center of a partisan maelstrom as it investigated Hillary Clinton’s use of a private email server and then President Trump’s election campaign. Officials knew that when they were drawn into the Kavanaugh matter, their work was destined to become mired in politics and leave many feeling unsatisfied.

Because agents were tasked with performing a background check rather than a criminal investigation, the scope of their work was decided by the White House, which seemed to be taking significant direction from Senate Republicans. The FBI never planned to draw any conclusions about the credibility of the allegations or Kavanaugh’s worthiness as a judge — which are questions left for the White House and Senate.

Initially, the FBI was asked to interview four witnesses. Three — Mark Judge, Peter Smyth and Leland Keyser — were at the gathering where Ford said Kavanaugh pushed her onto a bed and groped at her. The fourth, Deborah Ramirez, had separately alleged that Kavanaugh exposed his penis to her when both were students at Yale.

The limited breadth, though, sparked significant controversy, and the White House soon permitted the FBI to expand its investigation — albeit only modestly. The White House, for example, barred a broad look at Kavanaugh’s youthful drinking and whether he had misled the Senate in testifying about it, the people familiar with the process said. Some Republican senators insisted Thursday that the FBI was allowed to interview those the agency deemed appropriate.

“The FBI has gotten all the permission they need in order to interview whoever they think is necessary,” Sen. John Cornyn (R-Tex.) said at a news conference.

Agents also talked to two other men, Tim Gaudette and Chris Garrett, who were listed on a calendar as being with Kavanaugh at a gathering at a house on July 1, 1982.

The calendar entry had fueled some speculation that the gathering might have been the one at which Ford claimed to have been assaulted, though the list of attendees did not match those she had recalled being in the house when she said the attack took place.

The bureau also interviewed three other people, whose names have not yet been made public, according to the White House. Notably, though, agents did not talk to Ford herself, nor did they interview the more than a dozen other people whose names Ford’s legal team provided to the bureau. The legal team said those people would have challenged the credibility of Kavanaugh’s Senate testimony or provided other information to support Ford’s account.

If agents had interviewed those people, a member of Ford’s legal team told The Washington Post, they might have learned that Ford was never focused on July 1 as the date that the assault occurred.

Ramirez’s legal team, similarly, said that it provided the FBI with a list of more than 20 possible witnesses and that it was unaware of the FBI following up with those people. Several former Yale students have said they got in touch with the FBI proactively offering various bits of information but were never formally interviewed

William Pittard, Ramirez’s lawyer, wrote to Wray on Thursday, saying that those people were still available to talk.

“There may be additional witnesses who could offer still further corroboration (if any additional corroboration were needed, which it is not). But we likely never will know, given that your agents were barred from investigating,” Pittard wrote.

The FBI spoke with Judge about the claims of a third woman, Julie Swetnick, who said in a sworn declaration that Kavanaugh was physically abusive toward girls in high school but not to Swetnick herself. Her attorney, high-profile Trump rival Michael Avenatti, tweeted Thursday that the bureau’s investigation was “no investigation at all.”

Sen. Dianne Feinstein (Calif.), the ranking Democrat on the Senate Judiciary Committee, said the FBI report seemed to be “a product of an incomplete investigation that was limited, perhaps by the White House.” Senate Minority Leader Charles E. Schumer (D-N.Y.) called for the public release of the FBI’s findings, a copy of which senators were taking turns reviewing in a secure area of Capitol Hill on Thursday.

The Democrats’ frustration, though, might not amount to much. While Collins praised the investigation as apparently “thorough,” Sen. Jeff Flake (R-Ariz.), considered another key swing vote, said he had “seen no additional corroborating information.”

Emma Brown and Tom Hamburger contributed to this report.