If the allegations could be proven true, I think that the current climate around this behavior (even though as 17 year old), along with the politics that drive today's decision-making, would put an end to Kavanaugh's confirmation chances. But the accusers credibility should be at issue, and given the circumstances, if there is no corroborating evidence, I think he should be given benefit of the doubt.
Makes me think though, that a short while ago (a little more than 15 years ago), a very credible witness, Anita Hill, testified openly in front of the US Senate that Clarence Thomas engaged in some pretty disturbing sexual harrassment. Today, it's still very difficult for me to believe that she made it all up. Yet, just 17 years ago, the US Senate either didn't believe her or didn't think Thomas' actions were disqualifying. I don't think there is even a remote chance that Thomas would be confirmed if the same situation occurred today.