Watch the whole interview. He's just choking on his saliva. Or post-nasal drip. Happens to everybody sometimes. He takes a sip of water and is back to normal, no nervousness, no more rapid blinking, answers questions calmly and coherently. I've had this happen to me on conference calls too, and I'm sure I looked like a mess.

I'm not defending the guy, and I think there is more going on here, but this is just a very short clip and it is taken out of context.