Does anybody know more about YouGov's methodology? On the face of it, I'm suspicious of their very low margin of error which seems substantially better than any other poll out there, but you can't deny that their polling was accurate.

Another thing that looks odd on that graph: the given polling numbers from Washington Times/Politico/Monmouth/Newsmax/Gravis/Fox/CNN/ARG all look identical despite their differing margins of error (which suggests their source data is different). What's going on there?