...knowing some day he might need it in a hurry.

I tend to believe his accuser. If I really wanted to stop his nomination*, I would be very aware that if my scheme was blown, not only would he get a free ride to office, but my cause would get totally discredited (not to mention I might wind up in jail!).

Still, political fanatics are not always known for their cool and rational analysis. Just think...Birtherism!

*EDIT: ...stop his nomination [for purely political reasons] I would be...

In other words, a purely political smear job with absolutely no basis in fact or evidence to back it up would have a very high probability of backfiring; not only against the witness, but whatever political philosophy she represented. Its a high-risk, low-chance-of-success strategy that could easily blow up in your face. Its not entirely impossible, of course, but I consider it highly unlikely. I believe this witness, but having said that, going after someone for something that he did decades ago when he was drunk in high school is not likely to get much traction.