From the Intercept:
The specific content of the document, which is a letter from a California constituent, is unclear, but Feinsteins refusal to share the letter has created tension on the committee, particularly after Feinstein largely took a back seat to her more junior colleagues last week, as they took over Kavanaughs confirmation hearings with protests around access to documents.
The letter took a circuitous route to Feinstein, the top-ranking Democrat on the Judiciary Committee. It purportedly describes an incident that was relayed to someone affiliated with Stanford University, who authored the letter and sent it to Rep. Anna Eshoo, a Democrat who represents the area.
Different sources provided different accounts of the contents of the letter, and some of the sources said they themselves had heard different versions, but the one consistent theme was that it describes an incident involving Kavanaugh and a woman while they were in high school. Kept hidden, the letter is beginning to take on a life of its own.
https://theintercept.com/2018/09/12/brett-kavanaugh-confirmation-dianne-feinstein/
Whatever happened in high school is now a disqualifying offense.
Dems dont care how old it is as long as it blocks Kavanaughs ascension to the Supreme Court.
Mission accomplished.