Judge Kavanaugh is not defending himself by saying (as some supporters of his nomination are) that he was just a kid back then, or that people can sometimes have differing memories of long-ago encounters, especially when they were drinking. He has instead made a categorical denial, going so far as to say, according to Senator Hatch, that he did not go to any party meeting Professor Ford’s description.
The emergence of any evidence that contradicts that denial would end his nomination and probably his current judgeship. Assuming Hatch is right about what Kavanaugh is saying, all it would take is another person’s saying, I remember being at a party with Kavanaugh that sounds like the one Ford is talking about, and it’s over.
And it should be over at that point. As Lyman Stone points out, Kavanaugh’s defense destroys whatever force the he-was-just-a-kid argument ever had: He’s an adult now, and evidence disproving his blanket denial would mean that he is lying — and thus smearing Ford — now.
Even Kavanaugh’s most contemptuous critics have to concede that he is a smart lawyer. Even Paul Krugman, here being his worst self, would have to concede that. The judge has to know the implications of what he’s saying. A possible explanation for that tack: He is very confident that no evidence to undermine his categorical denial will come out.