here's an experiment where they gave 4 different pollsters the exact same data and they all came up with different results. just shows you how the data can be and is manipulated. that doesn't even take into account getting garbage into the poll in the first place. so you're relying on a poll getting unbiased information in and then having them interpret it correctly. it's a crap shoot
http://www.nytimes.com/interactive/2016/09/20/upshot/the-error-the-polling-world-rarely-talks-about.html?_r=2