Robert Jones and Daniel Cox examine support for civil unions over time:
The changing political composition of civil union supporters shows that the center of gravity of this debate has shifted significantly. The civil union option has moved from being a middle way dominated by political moderates a decade ago to one that is, today, most attractive to political conservatives. And looking ahead, there is evidence that the civil union option may have a limited future, at least if younger Americans are any indication. When given a three-way choice, civil unions are the least popular option among Millennials (Americans born after 1980). Only slightly more than 1-in-10 (13%) Millennials prefer civil unions, while 67% say they support allowing gay and lesbian people to marry, and 15% oppose any legal recognition of a gay couple’s relationship.