Confirmation bias is the influence of your beliefs based on your desire.
In this context you could think of it as "wishful thinking". You really want Kavanaugh to be disqualified as a SC justice, so you'll believe anything and suspend rationality to promote (within your own mind) anything that could make your desired result come true. When it turns out you were obviously wrong, you go with. "But I still believe he's guilty of something."
There is no evidence to support "this wise ass has plenty of impropriety in his past" but it's your last refuge after failing with silly shit like the sexual misconduct in high school stuff. A rational person would recognize the fact that the dems couldn't find anything, therefore he's probably a pretty okay guy.