Politicians and pundits from all quarters often lament democracy's polarized condition.

Similarly, citizens frustrated with polarized politics also demand greater flexibility from the other side.

Decrying polarization has become a way of impugning adversaries. Meanwhile, the political deadlock and resentment that polarization produces goes unaddressed. Ironic, right?

Commentators rarely say what they mean by polarization. But if Americans are to figure out how to combat it, they need to begin from a clear understanding of what polarization is.

My forthcoming book, "Overdoing Democracy," argues that polarization isn't about where you get your news or how politicians are divided – it's about how a person's political identity is wrapped up with almost everything they do.