Yahoo News has an article from The Week that purports to tell you all you need to know about understanding polls. While a bit oversold, it does give good information. One bit of wisdom the article imparts that I'll share with you:
Elections aren't between parties; they're between candidates.
In other words, be careful with so-called "generic ballot" polls. In most elections incumbents win. Let's look at why.
If you ask people about the public schools, they'll tell you they are awful. Whereas, if you ask them about their own public school, they'll say it is great.
A generic political poll can be like that. This year you might have people telling pollsters that nationally the Democrats are awful, but thinking the one who represents my district is okay.
The real question is will this be like "most elections" or will it be a wave? In a wave, incumbents often lose. NOvember begins to look like a wave.
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This article has the normal MSM bias, for example when it says:
Real-life Republicans are less appealing that [sic] "generic" ones.
Question: why wouldn't this be as true of Democrats as it is of Republicans? Because the biased anonymous author finds Democrats live up to their "generic" billing?
Answer: real-life anythings are less appealing than "generic" ones.
One reason: most politicians are attorneys.