I have been looking at different poll aggregators a lot. I like Real Clear Politics, mostly because they don't use LOESS but more generally because they use simple averages. I like simple and transparent. The one question is which polls to average.
My guess as to their rule would was: no internet polls (definitely the case) and no partisan polls (counting Rasmussen as non partisan because that's what Scott Rasmussen says).
I was wrong. I now see that they have no rule. Sometimes they include PPP and some times they don't.
for Ohio yes
Nation wide no
One of the national PPP polls which they ignore is a tracking poll. There is no risk of selective publication. There is no justification for ignoring it while reporting other PPP polls.
The choice isn't between silly rules (LOESS smoothing and trend extrapolating) fancy rules (Nate Silver) or simple rules. It is between silly, Silver and arbitrary.