Answer:
Stratified Random Sampling
Explanation:
Take note, we are told they randomly selected from "50 potential voters from a list of registered voters in each county in a state." This course of action by the polling firm follows exactly the Stratified Random Sampling type.
The Stratified Random Sampling method involves a deliberate division of a research population into strata or smaller sub-groups.
So in this case, the state was divided into strata or smaller sub-groups, that is, according to each county.
