What happens when a vocal minority thinks it’s a silent majority?

According to a new survey by the Public Religion Research Institute, only 41 percent of Americans oppose allowing same-sex couples to marry. But that same 41 percent has a highly skewed perception of where the rest of the country stands: nearly two-thirds of same-sex marriage opponents erroneously think most Americans agree with them. And only two in 10 same-sex marriage opponents realize that the majority of Americans support marriage equality.

What’s going on here? For starters, Americans overall don’t realize how widespread support for same-sex marriage has grown -- only 34 percent of the public correctly believe that most of their peers support gay marriage. This is at least partly a function of how rapidly public opinion has shifted. Ten years ago, only 32 percent of Americans supported same-sex marriage, compared to 53 percent in favor today -- a 21-point shift.

But same-sex marriage opponents are unique in the depth of their misunderstanding of the issue. Because they skew strongly conservative and deeply religious, this may be a manifestation of what Andrew Sullivan has termed "epistemic closure." Think of this as an extreme case of confirmation bias -- that tendency of people to filter out information that challenges their beliefs and preconceived notions.

Epistemic closure was most publicly and hilariously on display during Mitt Romney’s 2012 presidential bid, when conservatives "unskewed" the polls to tilt the data in their favor, and the GOP establishment appeared to be blindsided by an electoral result that many independent observers saw coming months earlier.

The PRRI survey data show that among much of the GOP base, epistemic closure is still very much alive and well. And this fact is crucial to understanding the "religious freedom" legislation cropping up in places such as Kansas and Arizona. On the surface, it makes little sense to codify discrimination into law when public opinion has shifted dramatically toward equality and the courts are following suit.

But by and large, this is not the reality same-sex marriage opponents are living in. In their understanding, public opinion is on their side and they are literally only one court ruling, one "religious freedom" victory away from stirring the silent majority into action and turning the marriage equality clock back by about 30 years.