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It is a deliberate abuse of methodology to ask any eligibility question of a respondent other than whether they are, or are not, of the targeted group (adult/likely/registered.) If they are not of the targeted group for the poll, their answering of the phone -- even if they refer you to someone in the household who is a member of the targeted group -- has to be corrected by an appropriate factor for refusals.

When a poll is cited as having a ±3% MOE, it means nothing more than that you can say with 95% confidence that the mean answer for the sample population falls within ±%3 of the entire population of that cohort -- IF the sampling mehtodology is truly random. That is all it means.

It has no mathematically rigorous predictive ability, despite its being labelled "scientific" because it is nothing more than an indication of how that cohort would vote if they were voting today. It is of little practical predictive ability because the cohorts: adults ≠ registered voters ≠ likely voters ≠ people who will vote on election day ≠ people who will vote on election day and honestly answer the question of how they voted.

This is why Gallup has dropped out of the presidential polling business: in order to be useful, your model must be able to turn your target population into the actual voting population, and there is no mathematically, statistically, or even psychologically sound methodology for doing that. "Likely" generally "seems" better, but even that varies with the quality of a pollster's special sauce. The degree to which "likely" is properly modelled to extrapolate to voters-on-the-first-Tuesday-of-November is entirely a crap shoot which no polling organization has mastered for more than two elections in a row.

Fred, your post is a great explanation of polling. Every Freeper should read it. I personally think the turnout models this year are going to be way off. I’m sure most pollsters think that a 2008/2012 based turnout model is the way to go, but I don’t think Hillary is going to get anywhere near the black/hispanic support Obama did. Not saying it’s going to go for Trump. I think a lot will stay home. Also, Trump is going to get support from white voters, especially middle aged and older white voters, in unprecedented numbers. Groups like Bikers for Trump and the alt right are registering old white guys who’ve never voted before by the tens of thousands. Those guys aren’t the type to answer a poll and, even if they do answer, are unlikely to make make it through a traditional likely voter screen, so they won’t be counted.

2008 was hard to poll because of the first black candidate, so polls using 2000/2004 turnout models oversampled McCain’s support. 2016 will be even more difficult.

As you know, a poll is only as good as its turnout model, and recent polls have done a lousy job at predicting who is actually going to vote, Brexit being the most recent example.