in all the polls I've seen so far Allen is way down the list in name recognition and he isn't catching on. He is young and I think he will make a great candidate, in the future, but if he were to be Veep first I think his odds of being elected go up significantly.
As a VP candidate I see him as a positive for whoever runs at the top of the ticket, because he is likeable and personable -- definitely not a John Edwards-type that grits on you after a very short while.