I find it funny that people make such a big deal about +1 Obama or +3 Romney when there's a margin or error of like 5% for some of these state polls. Then again if you don't ignore that margin of error I suppose nothing much has changed in the last several months, and that's no fun.
Yeah, pretty much. It really depends on the poll though. Some are pretty consistent, so you can track changes and say reliably that so-and-so is doing better/worse than a month ago. Others swing widely, so it's not just the margin of error you have to look at but longer term trends in said poll. But both kinds are only semi-effective at actually telling us how an election might turn out. And in this election, the methodologies are presenting us with a really big factor that usually isn't so huge. Obama energized a *huge* number of people in 2008 to turn out and vote Dem. Normally, the participation rates don't change much between elections, but it did that year. You really have to consider it an outlier in terms of Dem turnout. But polls don't change their methodology to account for this (because it's important for them to continue using the same formula every time, for obvious reasons).
You can see this when you look at RCP average polling. You'll see about half that show the candidates within a couple point spread (some with Romney up, some with Obama up, but all close), and another half that have Obama up by 5-8%. When averaged, those give a 2-3 point lead for Obama. But garbage in, garbage out, right? You're generating an average where a significant portion of the data being used is quite obviously not going to be accurate. But those are the numbers, and those are the methods used, so they continue to use them.
Can't measure the exact effect of this, but you could almost safely say that any poll that uses this methodology (at any point in their process) is likely to be off by 5+ points. You could even stretch that (if you wanted to really crunch numbers) and speculate that they could be off by as much as 10-12 points. This could result in anything from a very tight win for Romney, to a landslide for him. In any case, it's almost certain that a whole lot of people are going to be surprised by the actual election results and wonder why they were so different from the polling data they were counting on being true.