Fascinating look (at least, to me) at how the USC/LA Times poll is possibly off. Apparently the polling panel includes a 19 year African American male* Trump supporter, and since its a set panel (that is, they are using the same group of people for each poll throughout the election) and since the poll weighs for things like 18 - 21 year old men, this one guy is distorting everything. As explained in the article, weighing usually doesn't get that targeted.
I do still think that the set panel poll strategy might have value as a trend poll rather than a level poll.
*Edit - in Illinois of all places....
No Gary Johnson in the poll?