Researchers examine the factors that influence whether a state will or will not adopt voter identification laws. They then analyze the effects these laws have on voter turnout in elections. They find that a unified republican government (that is, a government where republicans control both houses of state legislature and the governorship) is 16 times more likely to adopt voter ID laws than any other configuration of government. Additionally, having any part of government controlled by republicans significantly increases the likelihood of adopting ID laws. They further find that the effect a republican government has on the likelihood of adopting ID laws is decreased as the population of minorities grows. Further, they find that a state having voter ID laws did not produce any discernible effect on the probability that whites, blacks, or Hispanic citizens voted.
These results suggest that republican governments are much more likely to pursue policies that require photo-ID to vote. While other studies have suggested otherwise, the authors argue that these policies do not appear to disproportionately suppress minority turnout.