If a majority of idiots are conservative, that says much about idiots, but little of conservatives. If there are for more conservatives than idiots, it only tells us stupid people will probably tip the balance when liberals and conservatives are near equilibrium, not that conservatives as whole tend to be stupid.

Think of it as a Venn diagram like any large demographic within a much larger general population. A majority of women are Democrats, but if that makes all Democrats women why has every Democratic president been male? A majority of white Protestant males are Republicans, but Clarence Thomas is a black Catholic.

In terms of policies, one reliant on "the stupid demographic" to win is probably unwise, or a majority of intelligent people would not support an opposing one. However, that does not make the policy itself, or most of its supporters, stupid. It just means the policys overall popularity depends on disproportionate support from stupid people IN ADDITION to intelligent supporters. The latter still number in the tens of millions; they are just less numerous than the other policys intelligent supporters.

So IF (a big "if" at present) other studies corroborate this general one, it would be a good argument against conservative policy. It would mean stupidity encourages conservatism, whose electoral success relies on that. It would NOT mean conservatism denotes stupidity, because a host of other unrelated things ALSO encourage conservatism, and a host of intelligent conservatives respond to those other factors.