The crosstabs are up now on the SurveyUSA poll and there's already one pretty clear explanation for the bizarre numbers. The party identification breakdown on the poll is 41% Republicans, 40% Democrats, and 16% independents.
A month ago SUSA found a 46-33 Democratic party identification advantage. Although it is possible there could be some shift after the Republican convention a 14 point shift strains credulity. PPP has found a Democratic id advantage of anywhere from 8-15 points in its general election polls, and I think Civitas has found an id advantage of 11-13 points pretty consistently.
I am not one to trash Survey USA- I think they are a top notch company, but we all have our bad polls and I suspect for them this is one of them. We'll have new numbers tomorrow.