You will notice this poll only called 1000 people nationwide. It was not limited to Catholics, which is probably who it should have been aimed at (not that we actually vote on theology).
When I was in graduate school we had to design polls and execute some of them in a “statistically scientific” manner. They way they work is that you select a population *(for example you pick a small town) *and you can get an accurate representation of the feelings of that town by calling a certain % of the population and asking them questions. On a nationwide basis, to get a statistically significant valuation you only need a couple thousand answers.