I think it is because she reminds many people of that pretty and popular girl they knew in HS who was a sports star, not a cheerleader, who married the local hunk who was a hard worker, who got the community to support her efforts to run a clean government, then took that same drive statewide and eventually got to be Governor. That shocked them to no end. They were shaking like 10,000 volts were passing through them shocked to see her on national TV. Her being nominated for VP put their own miserable and jealous lives in relief. Who knew the girl next door cleaned up so well and even they could see that she could give one hella speech.
Here the haters are mostly guys who are either wishing they dated someone like that in HS (or wishing they dated ANYONE in HS) or guys that still cannot get a date, much less a date with a superstar like that, and need to vent how much better they are than her.
Her admirers, on the other hand, usually DID date the prettiest and coolest girl in HS or college or wherever who wasn't a cheerleader, maybe even married them. They aren't threatened by hearing her out. They know that people like that are rare but when they happen to come into your life they make everything just a little bit more special.