This article makes the point...
http://articles.latimes.com/2012/sep/27/news/la-pn-pollsters-weight-surveys-20120927So yes if we see a polling party ID trend towards R it could indicate a Trump win, but that would be reflected in the over-all horserace number anyway. So again, party ID is an interesting number and should be shown. But it shouldn't be 'forced' by the pollster model and it shouldn't be the metric by which a poll should be judged. General trackrecord and methodology is a better guide (sample size, do they phone mobile phones, do they offer Spanish, etc.)