American Identity - and Acceptable Marriages - Now More Defined by Politics Than Religion

In the 1960s, acceptance of interfaith marriage (e.g., Catholic-Protestant, Christian-Jewish) was often in the teens or twenties. Today, more than a quarter of Americans are in interfaith marriages, and most parents say they would not be upset if their child married someone of another faith.
By contrast, partisan identity has hardened. In the mid-20th century, few cared much about marriages across party lines, but now about 35–40% of partisans say they would be upset if their child married someone from the opposite party. This suggests that identity today is more defined by politics than by religion - a reversal from roughly a half century ago.

I wonder to what extent that has to do with plurality. In American politics, if you want your vote to count, you have only two choices. In religion, you have dozens, not even including choices like atheist, agnostic or spiritual but not religious . In such a world, marrying across religious lines becomes increasingly probable given anyone you meet outside of church is probably of another faith. By contrast, meeting someone outside of a political rally still means you've got roughly a 33% chance of a political match: Dem, GOP, or no affiliation.

As institutions shape the categories available to us, they also shape our tolerance for crossing boundaries. Where institutions create many identities (as in religion), crossing them becomes ordinary. Where institutions collapse choices into two rival camps (as in American politics), crossing them becomes taboo.

It might also explain why politics is becoming more divisive. Politics is not - if it ever was - a matter of debating policy so much as a matter of identity. Stats from modern America suggest to me that you'd have an easier time persuading someone to change their faith than to change their politics.