Okay, so it used to be that Democrats didn’t particularly care if their daughter married a Republican and Republicans didn’t really worry about their son marrying a Democrat. That may no longer be true, at all, and it may be, in fact, that people are more hung up about the political affiliation of prospective sons and daughters-in-law than they are about their race.

At least, that’s the conclusion reached by researcher Shanto Iyengar, the director of Stanford’s political communications lab, and political scientist Sean Westwood. In fact, their testing revealed that people are more apt to discriminate against college scholarship applicants based on party than on race. And this phenomenon, which began showing up after the Reagan Revolution in 1980, has been accelerating in recent years.

It’s a very interesting article and I encourage you to read the whole thing. But it didn’t address the question I had in reaction to the findings.

What are the issues that are driving this?

After all, the researchers didn’t expect issues or policy to have anything to do with anything.

The results showed, as you might expect, that Democrats exhibit an automatic bias against Republicans, and vice versa. What was surprising was that the bias partisans exhibited for their out-group exceeded the bias white participants showed for black people, or that black participants showed for white people. According to the test, Americans are more automatically partisan than they are automatically racist. (If you want to know your own results on the racism test, you can take a version meant to test racial bias here.)

This was, to Westwood, a bit of a shock. “To be honest, I didn’t expect this to work at all,” he says. “The common story is most Americans don’t care about politics, they don’t understand politics, they don’t understand policy. So you wouldn’t expect Americans to have strong preferences. That’s where I started.”

But, for whatever reasons, it’s increasingly true that moms and dads see members of the opposite party as morally unfit to join their families by marriage. There must be real-world things that lead them to that conclusion.

Perhaps Republican parents can’t abide anyone who is supportive of reproductive rights because they see abortion as such an atrocity.

Perhaps Democratic parents can’t contemplate having someone to Thanksgiving who thinks torture is acceptable.

You know, maybe people have some pretty strong moral values and they see the other party as being completely immoral.

This is, I suspect, what has happened.

I don’t think differences about tax policy explain why the country has grown apart to such an alarming degree.

It’s probably true that the media has played a big role in making this happen, but this can be exaggerated.

Also, if these folks think the following is true, they need to watch more Fox News:

“Political identity is fair game for hatred,” he says. “Racial identity is not. Gender identity is not. You cannot express negative sentiments about social groups in this day and age. But political identities are not protected by these constraints. A Republican is someone who chooses to be Republican, so I can say whatever I want about them.”

You can see an example when you look at the media, Westwood observes. There are no major cable channels devoted to making people of other races look bad. But there are cable channels that seem devoted to making members of the other party look bad. “The media has become tribal leaders,” he says. “They’re telling the tribe how to identify and behave, and we’re following along.”

There are some ways in which MSNBC and Fox News are mirror images of each other. They both are, at least for a good portion of the day, devoted to making the other party look bad. But Fox News is also committed to making blacks look bad.

And they’re not much better when it comes to Latinos, Muslims, and folks who want a wedding cake for their gay wedding.