Theory: In the mid- to late 1960s we would debate that because the government was making abortion and contraception difficult to obtain that the poor and/or less fortunate would produce more children and the more wealthy and/or intelligent would produce fewer children.
Here we are three generations later, the poor and/or less fortunate tend to be less progressive and less interested in the overall future. These people are more receptive to conspiracy theories and lies, the perfect group for the Republicans to prey on.
When polled, the Republicans are far less educated than Democrats, making them less interested in research and more vulnerable to false information.
"If you make people think, they will love you. If you really make them think, they will hate you."