Arceneaux, Kevin (2005) "Using Cluster Randomized Field Experiments to Study Voting Behavior." The Annals of the American Academy of Political and Social Science 601: 169-179. doi: 10.1177/0002716205277804
Voter mobilization experiments are often conducted using individual-level randomization, which can be difficult to implement. A simpler approach is to randomly assign voting precincts, rather than individuals nested within them, to treatment and control groups. Not only is it easier and potentially less expensive to implement, it may allow researchers to study vote preference effects without collecting survey data. This article explores various methodological concerns that researchers should consider when designing and analyzing precinct-level experiments. These concerns are illustrated using data from a precinct-level randomized field experiment conducted in Kansas City, Missouri.
Link to article here.