Over at Balkinization, I’ve been blogging (here, here, here, and here) about the benefits associated with spillovers, which occur when one state’s policies affect citizens of another state. Most of those arguments have to do with my other field, federalism. But they are relevant to two debates in election law. First, to the extent that election law scholars are interested in the role that political parties play in safeguarding vertical federalism, a topic that has inspired great articles from both Larry Kramer and Jessica Bulman-Pozen, I speculate that political parties play an equally important role in safeguarding horizontal federalism. Second, to the extent that we are all worried about polarization and the “big sort,” interstate spillovers may provide a partial antidote to polarization’s worst excesses. That’s because they force all of us to live under someone else’s law. You might think that living under someone else’s law is a terrible thing because it violates the deep-seated democratic principle of self-rule. But democracy isn’t only about self-rule; it’s also about ruling together. Given our impulse to retreat into our all-too comfortable red or blue enclaves, it’s very useful for our worlds to collide now and then. Those collisions give us a chance to see how other people live, to live under someone else’s law, to try someone else’s policy on for size. Democracy, in short, requires us to do just what spillovers require us to do: Work it out. Sometimes we work it out directly. Sometimes we need a referee. Sometimes we just take our lumps and live under a policy we don’t like. And we do so for a simple reason: We’d rather live with other people than without them.