Take the survey with a grain of salt. It's an internet Survey Monkey poll. I've never heard of them before. This could be their first poll with NBC.
Monkey Survey is pretty common; usually conducted by a specific group and I'm sure polls reported by media groups would show different numbers. What most polls have reflected is the controversy over Trump, the spar between Chrisite and Paul which dropped their numbers, the rise of Cruz despite him being ignored during the debates and Fiorina now has recognition -- numbers vary from poll to poll. I have not seen any poll that shows Bush gained any ground ... but I'm sure if I looked hard enough I'd find one.
I take issue with debates as the moderators obviously have the ability and often do ask questions to benefit their "favorite". Cruz was pretty much avoided during the FOX debate, yet according to several polls he benefited. With the internet at the fingertips of most Americans I wish they would research a candidate's voting record and past performance to see where they truly stand on the issues rather than basing their opinion solely on the debates; failure to do so is why Obama get elected in the first place. His record as a Senator was far more accurate as to how he would perform as a president rather than the false claims he spewed during the debates.