Top candidates only, non-partisan polls only, likely voters only, graphic updated October 15th, most recent polls October 12.
Apropos of this topic (vis-à-vis U.S. presidential election predictability), there's an interesting view expressed in this Wednesday (10/14) blog from Reuter's:
Not sure "top" candidates is quite the right word given their quality. Then again "leading" or "highest" and least of all "best" hardly fit either.
Still reckon it'll be Jeb! Bush vs Hilary Clinton for the 2016 US elections but not as sure of that as I once was. Just such an unimpressive, crazy mob to choose from Repubs wise.