Most voters in North Carolina and the rest of America cast ballots reliably for either Democratic or Republican politicians — even if the voters themselves don’t belong to a party. That’s pretty much the definition of political polarization, and a well-established fact of current voter behavior.

But it is also obvious that voters don’t just come in two categories. There are Democrats who favor restrictions on abortion, Republicans who favor higher taxes on the wealthy, partisans who disapprove of their leaders’ personal behavior, and lots of disagreements across the two political coalitions on many other specific issues.

So what truly separates Democratic-leaning voters from Republican-leaning ones? According to the latest voter-typology study from the Pew Research Center, one of the strongest predictors of partisan leanings has to do with the size of government.

“If you had to choose,” the Pew questionnaire reads, “would you rather have a smaller government providing fewer services, or a bigger government providing more services?” In most of the recent past, smaller government has been the more popular answer to this question, although this year the responses have been closer to even. More to the point, the response bear a strong relationship to party preference.

The 2017 Pew typology of voters consists of eight different voting groups — two core Republican constituencies, two core Democratic ones, two that lean Republican, and two that lean Democratic. I don’t have room here to describe these eight typologies in great detail, but perhaps thumbnail sketches will suffice to make the point.

On the Republican side, disproportionately upscale Core Conservatives and disproportionately rural Country First Conservatives are the most reliable GOP voters. Their primary areas of disagreement are on foreign policy, trade, and immigration. Two other groups, the mostly pessimistic Market-Skeptic Republicans and the mostly optimistic New Era Enterprisers, contain lots of unaffiliated voters and express plenty of disagreements with the Republican platform. But they vote Republican most of the time.

On the Democratic side, Pew calls the most loyal groups Solid Liberals (disproportionately wealthy and secular) and Disaffected Democrats (disproportionately poor). A third group, Opportunity Democrats, are notably more optimistic about the future and favorable to business than the first two. Slightly more of them identify as unaffiliated or leaners than as Democrats. A final group, Diverse and Devout, is just what the name implies — racially diverse, older than average, and often in disagreement with Democrats on social issues and other matters. Still, most vote blue most of the time.

Political junkies love to read and digest these kinds of studies. They are typically drawn to the differences, the variations, the surprises.

I freely admit to the same bias. I was fascinated to discover from the new Pew data that only one of the four GOP-leaning groups, the Country First Republicans, is clearly opposed to same-sex marriage. Another notable finding is that the Democratic groups are starkly divided on how much America ought to be engaged in international affairs and whether regulations on business do more good than harm.

But when it comes to the size of government, the two coalitions are easy to differentiate. All four GOP groups say they want smaller government, by at least a 22-point margin (Core Conservatives are nearly unanimous at 93 percent). All four Democratic groups say they want larger government, by at least a 21-point margin (Solid Liberals are solidly in favor at 80 percent).

Naturally, there are tensions between what these voters say they want in abstract and what they favor in particular instances. Nevertheless, what the government-size question reveals is that the broad philosophical differences are real and politically significant.

For the foreseeable future, Democratic politicians will talk a lot about how government programs help people and solve problems. Republican politicians will talk a lot about how government programs often cost more than advertised and make problems worse by producing unintended consequences. Politicians will say these things because they believe them, for the most part — but also because those are the messages that unify their respective electoral coalitions.

John Hood is chairman of the John Locke Foundation and appears on the talk show “NC SPIN.” You can follow him @JohnHoodNC.