RALEIGH – If you see the two major political parties as more polarized and more ideological than they used to be, congratulations! Your Spidey sense is working. But let’s be sure to interpret those tingles accurately.

According to a new survey from the Pew Research Center, Democrats and Republicans are further apart today than they were in the past on many issues. The gap is particularly wide on welfare spending and environmental regulation. The average Republican is much less supportive of these policies today than the average Republican was in 1987, while the sentiment of the average Democrat hasn’t changed. The gap between the two parties on welfare support went from 23 percentage points in 1987 to 41 points in 2012. The partisan gap on environmental regulation is now 39 points, vs. only five points in 1987.

But it isn’t just that the average Republican has moved rightward. The average Democrat has also moved leftward, particularly on social policy. When asked if “we should make every effort to improve the position of minorities, even if it means preferential treatment,” a majority of Democrats today say yes, vs. only a third in 1987. Few Republicans say yes. The gap on this question is now 40 points, compared to 18 points in 1987.

Keep in mind, however, that we are talking about average differences between the two parties. These findings do not show Americans as a whole to be more hostile towards each other, or to hold more “extreme” views, or to have moved rightward or leftward overall during the past 25 years.

What really happened is a sort of political Big Sort. Conservatives who used to be “boll weevil” Democrats have now become Republicans. Liberals who used to be “gypsy moth” Republicans have become Democrats. And many moderates who used to identify as partisans now identify as independents.

In short, the political brands “Democrat” and “Republican” convey more ideological information. By the conventional definition, most partisan Republicans are conservatives. That wasn’t always true.

North Carolina is an excellent place to start if you seek to understand the causes and consequences of the Big Sort. For most of our political history, regional and cultural factors played a major role in determining party affiliation. If you resided in Eastern North Carolina or large swaths of the Piedmont, you were almost certainly a Democrat. If you resided in parts of the western Piedmont and mountain counties that were settled overwhelmingly by subsistence farmers rather than slaveholders, and felt slighted by Raleigh, you were probably a Republican.

Regional and cultural factors explained party affiliation elsewhere in the country, too. There were parts of the Northeast and Midwest where anyone who wanted to be part of the establishment joined the Republican Party – regardless of the person’s views on taxes, defense, abortion, or education. Similarly, there were strongly Democratic places on the coasts, in big cities, and in the rural South where becoming a Republican was considered unthinkable.

As a result, the two parties were coalitions within which very different political constituencies clashed. North Carolina has long had competitive statewide elections for governor and U.S. Senator, for example. But until the 1970s, they occurred in the spring, on the day of the Democratic primary, rather than in the fall election against token GOP opposition.

Since the 1970s, however, the two parties have become more ideologically consistent. There were many reasons, among them generational change, individuals moving to other states (or from other nations), and active pressure by activists to hold politicians accountable for votes. Labor unions and abortion-rights groups withheld support from wayward Democrats. Anti-tax groups and social conservatives withheld support from wayward Republicans.

As a result, the two parties got smaller and more coherent. Independents now make up 38 percent of the electorate (though the “true” swing vote is 12 percent, if you subtract independents who lean D or R). They tend towards a mixture of political views.*

It’s hard for me to see this as bad news. Distinct party brands have given voters more information, and made Tar Heel politics more competitive, especially down the ballot. Swing voters still tip the balance. I think we’ll survive the Big Sort.

Hood is president of the John Locke Foundation.

* Corrected from the original version, which stated the unaffiliated share of total voters at one-quarter.