Just as the perjury case against President Clinton hinged on the definition of the word “is,” the leftist campaign to paint Supreme Court nominee Brett M. Kavanaugh as a lying, ice-throwing hothead could depend on how you define “boof.”

As the sexual misconduct allegations against Judge Kavanaugh remain stubbornly uncorroborated, the Democratic effort to derail his Supreme Court nomination has switched gears to more subjective criticisms of his temperament and descriptions of his youthful partying.

“Thursday’s hearing provided fresh examples of Judge Kavanaugh’s difficult relationship with the truth,” Senate Minority Leader Charles E. Schumer, New York Democrat, said in Tuesday floor remarks. “Judge Kavanaugh gave answers about his yearbook page, supposed drinking games and high school behavior that simply defy credulity.”

Sen. Bernard Sanders, Vermont independent, called for the FBI to investigate Mr. Kavanaugh’s testimony before the Senate Judiciary Committee, including the judge’s assertions that he never suffered memory loss after drinking and that a reference to “skis” on his 1982 high school calendar referred to beer.