On the other hand, the national and other state surveys? I've been saying to ignore them. And here's some nice evidence for it. Nate Silver has been crunching the numbers for a primary/caucus election forecaster, only to find, first, that a polling-based forecast more than thirty days out is hopeless, and then:
The model also makes a special provision for Iowa and New Hampshire, which can have an especially large influence on the race. A New Hampshire poll conducted one day after the Iowa caucuses will receive considerably more weight than one conducted just one day before Iowa. In practice, this means that the first New Hampshire polls conducted after Iowa will all but eliminate those conducted just before it.There are usually eight days between Iowa and New Hampshire; this year they are a week apart. And post-Iowa polling will make pre-Iowa polling obsolete? Yikes!
I should explain...that doesn't necessarily mean that pre-Iowa polling in New Hampshire doesn't predict NH primary results at all. It just means that if post-Iowa polling is different (which may or may not be the case) that at that point you want to toss the pre-Iowa numbers. Presumably, the pre-Iowa numbers predict the post-Iowa numbers, at least better than starting from scratch would. Got that?
What I'd love to see Silver plug into his equation is whether Iowa polling helps predict New Hampshire (and other states). I suspect it wouldn't work -- what matters is the spin from Iowa, not necessarily the results, and even then Iowa polls aren't really a reliable enough guide to Iowa results for it to (probably) work. But I think it would be worth it to try running it, anyway.
Anyway, back to the main point: if polls more than 30 days out are useless right now, then national polls, too, are useless as predictors. I want more Iowa polls, precisely because the chances that the ones from only a week ago could already be useless, and because Iowa affects what comes next. And I'll sort of at least glance at New Hampshire polls beginning about now. But the rest of them? Ignore those polls!