I really dont understand these polls, most of the other polls are the opposite. Either the polls are complete junk, or we are being deluded.
hell 538 has her WAY ahead :(, i know that isnt a poll but thats a damn big spread. At least if it was 60/40 or something you could say ok good shot MOE or something...
I think the problem with polling is multiple fold.
1) Getting the right sample. Landlines were historically the best way but now only about 60% of the country has a landline, only 7% of people respond to calls and around 30% of people lie about their intention on whether or not they will vote
2) You can take your subgroups from #1 and then forecast an electoral mix by demographic based on response from #1 but that typically assumes turnout similar to the last couple of elections which may or may not be the case.
3) Internet polling - same issues - you have to have the right email database of a representative sample, get those people to agree to take the poll and then weight them proportional to your expected demographic turnout.
That doesn't even count issues like the Bradley effect among others. It's an art as much as it is as science.