It is very likely that Feinstein knew in July, when her constituent sent the allegation to her, that it was so lacking in any kind of detail and backup that it could not derail Kavanaugh. But that didn’t mean that the allegations from Christine Blasey Ford could not be politically useful.
By releasing the information at the last hour, Feinstein put Republicans on the judiciary committee and the White House in a catch-22. They could either vociferously defend Kavanaugh and look like they were once again defending an abuser of women, or throw him under the bus and have to scramble to nominate and confirm a new nominee.
If, as increasingly appears to be the case, the GOP stands behind Kavanaugh in the face of this allegation, Feinstein has created a Me Too moment that Democrats can campaign on in their attempt to take back Congress, just as she did in 1992. It is, in a word, brilliant. One can almost see Mitch McConnell smiling and fist-bumping her, saying, “Well played, Di.”