There were examples of very large polls that failed spectacularly because of the badly chosen samples https://www.math.upenn.edu/~deturck/m170/wk4/lecture/case

There were examples of very large polls that failed spectacularly because of the badly chosen samples https://www.math.upenn.edu/~deturck/m170/wk4/lecture/case1.html https://www.math.upenn.edu/~deturck/m170/wk4/lecture/case1.h...