The old saw "statistics lie, and liars statistic..." wait, that's not it, "fool me once....won't get fooled again"...mmm, overused and off kilter..... maybe.... "It's just 3dB error", e.g. off by half - that's it.

Polls are popular - search hard enough, you're bound to find one that supports your cause. And if not, you can always complain about accuracy, number of people, leading questions and push polls, land lines vs. mobile, etc. But whether pro or con, polls typically sample 1/1000th or less of the final population. I.e. "a spit in the ocean" in modern parlance.

When they say "within a sampling error of plus or minus 5 points", I don't think that means what you think it means - I believe it's "our process is 95% repeatable", and sure as hell don't mean "accurate to within 5%", judging from deviances of 20% or more between polls

Let's look at the polls. 10 days before South Carolina,  so-called respectable CNN/ORC had Clinton up by 18%. The RealClearPolitics average was 27.5%. Hillary won by 47.5%. The *average* of polls taken over the prior two weeks was *twenty percentage points off*.  It would have been much worse, but Clemson published a lone poll predicting a 50 point spread, only slightly high.

The Virginia GOP polls had Trump up by a spread of 14.5% - he won by only 2.8%, about 12% difference.

So I'm supposed to make a decision based on hypothetical polls 8 months in advance, when they have trouble with elections 2 weeks away?

Worse, since Gallup and Harris and other big names dropped out of the election polling business, it's gotten more and more inaccurate, with fewer extensive polls to go by. Everyone's copying 538 by averaging now, though not necessarily weighting them, but there's a great acceptance of "no matter how inaccurate we are, they'll forgive us and forget after the actual election". So little drive-by hit pollsters can flourish among the more dedicated and believable.

More I have trouble with many people preaching "electability" - they typically don't know what they're talking about, or at least their arguments point in the wrong direction. Even if the mood of 1000 people reflected the vote of 150 million voters 8 months later, *THAT'S NOT HOW US ELECTIONS WORK*.

Obama beat McCain by 7.4% of the vote. He won the electoral vote by over 2 to 1. That latter figure is what matters. Al Gore won the popular vote over George W. Bush. But the election tilted to Bush not over a dispute about raw numbers, but electoral votes in one particular state.

In 2008, only 14 states were within 10% difference, only 6 states were within 5%.

In 2012, Obama won with 3.8% vote total, but a 3:2 electoral vote advantage: 62% to 38%, 24% difference. Only 3 states were within 5%, 17 within 10%.

There's a good chance that in states with more than 10% difference they could put a comatose pedophile with a skin disease and he'd still win. The only thing that matters are likely 10 to maybe 17 swing states, max 1/3 of the nation. Realistically, much less. 

As for "likely voters" in the electability argument, I don't get it - Bernie isn't able to convince more conservative & moderate Democratic southern voters, but I should be happy that he "gets 25% of the republican vote in his state and attracts the largest share of independents" - are those people I want to attract? I thought they were tea baggers and survivalists and racial supremacists and other kinds of cysts. In that case, why not put Trump on our ballot too, so we can win at all costs - yay!!!

Here's Obama, looking cooler than ever (think he's taking on Bill Cosby's standup routine since he won't be needing it anymore), laying out the difference between Democratic wishes & achievements and Republican delusions. It'd be nice if we tried to keep that divide while unifying the party. We're supposed to be the reality-based side of the aisle - whether global warming, healthcare, gun control, foreign policy or election possibilities. Fight hard, dream hard, but keep your feet on the ground - don't succumb to the Madness of Crowds nor the "Science of Big Impressive Sounding Numbers".