Here's an interesting article at the Neuroskeptic blog. It's about Pathological Déjà Vu.

You know what déjà vu is: that creepy feeling we all get sometimes, when we're in a place or a situation we've never been in before yet which seems familiar. Well, in some people it's a chronic disorder. Every place they go, everything they see or hear, seems weirdly familiar.

To sufferers from pathological déjà vu I extend my sincere sympathy. I know how they feel. I get that same disorienting sensation every time I see Mrs Clinton on TV.