That clip is less than a minute of an interview that was a half-hour long, FYI. Plenty of the interview went fine, and he definitely seemed more comfortable in most of the interview than in those particular 40 seconds.
Anyway, Sanders doesn't seem to be taking much rest after 5 rallies. He'll have another 3 in the next four days. Two tomorrow in NH, and one in SC on the 14th (good to see that he's not going to be writing off SC this time.) Even those who don't like him have to admit, it's impressive that a 77 year-old can do this many rallies in such a short period of time.
Not surprising at all.. this man runs to catch his train.