No one wants vote fraud and no one wants voter disenfranchisement. Voter ID requirements are meant to find a path between these two competing problems. If you follow the political debates on this topic, you will see every Republican more concerned about vote fraud and every Democrat more concerned about voter disenfranchisement. The reason for this divide is rather obvious: the segment of the population most impacted by voter ID laws overwhelmingly votes Democratic, so it is in Republicans’ interest to allow as few votes as possible from this segment and in the Democrats’ interest to allow as many as possible. This is a scenario with an obvious surrogate variable.
Many universities have a strong belief in the value of a diverse student body and strive hard to achieve this diversity. Race is one axis along which most universities desire diversity. However, laws limit direct consideration of race. However, there usually are no limits on indirect considerations of race through other variables that may be highly correlated with race. Indeed, many universities have found legal ways to achieve diversity.
In short, there often are other variables that can be considered, if desired, in lieu of variables that are disallowed. Doing this manually is not easy. Computers can do this really well, though. But computers can also measure how well they are doing. And we can require computers to make sure they don’t choose combinations of variables that are “too good” as surrogates.