Take the current value of the dow jones, round it to the nearest dollar. Then create one hundred letters, each of which says "The dow jones will be at X, one week from now." where X is the current value plus or minus increments of 5 dollars up to +250 and -250. Then add some sort of hook to the end of the letter such as "If you would like to learn my secrets of predicting the stock market you can take my course for the reasonable cost of Y dollars." Then print out 100 copies of each letter and send them to random folks, perhaps some number of people who receive letters that end up accurately predicting the stock market will fall victim to your scam.
That's the same problem we're dealing with here. Presidential votes only happen once every four years, so it can be difficult to validate any sort of model. A hundred pundits make a hundred different predictions. And dozens of polls make different predictions as well. Does that mean that the pundits and the polls which ended up being closer to the truth are more accurate or does it just mean that they were lucky?
That's the same problem we're dealing with here. Presidential votes only happen once every four years, so it can be difficult to validate any sort of model. A hundred pundits make a hundred different predictions. And dozens of polls make different predictions as well. Does that mean that the pundits and the polls which ended up being closer to the truth are more accurate or does it just mean that they were lucky?