http://www.independent.co.uk/news/u...st-who-will-win-results-populus-a7097261.html
You can read the polls here. The YouGov one was only 2 so that might be one you saw however that was an online poll that normally favors Brexit.
There's loads of primaries they predicted him to lose and he swept them all but ultimately the only poll that matters is the election.
I'm not sure his job was to win over undecided voters although that's what people say. It looks like he went in with the strategy of getting out his base and in particular the Tea Party/Evangelicals who he has seen his support drop with due to the sex scandals - which has been the reason for his drop in the polls. If he can get them back then he's within 1 or 2 points like before and after that it's turnout and he will win if it comes down to turnout.
There's not many ways Trump can win. He needs to maximize everything but it's still possible if he can win those back and his stance on both the 2nd Amendment and abortion will have helped him greatly plus I think he did an excellent job with the sex scandal basically saying you can't trust Hillary which people can't.