Notice that unlike today's polls, this one does not mention the "margin of error" (nor the sample size). That may be because the concept of "margin of error" was not accepted until after WWII, famously when the technique accurately predicted that Truman would defeat Dewey in the 1948 presidential race, when most polls/models predicted otherwise. Leslie Kish pioneered the concept. It amazes me that such a fundamental concept was only just "invented" in such recent times.

Unfortunately, I'm afraid that today's popular news readership still doesn't pay much attention to these concepts, and thus accept poll results at face value. This poster, even with its flaws, would probably still have influence over the populace today.