Has politics become polarized? Even if you and I agree on little else, I’ll bet we agree that the answer is clearly yes. But as the wild and wacky elections of 2018 near their close, it’s worth considering what political polarization is — and what it is not.

Not that long ago, a significant share of voters split their tickets between the two major parties. They voted for Republican candidates for president and other federal offices, for example, even as they were perfectly willing to elect Democrats to state and local offices. That was a familiar pattern in Southern states.

Elsewhere, in electorates such as the Northeast corridor and some Western states, ticket-splitters often went the other way: Democratic for federal office, Republican down the ballot.

Here in North Carolina, as many as a quarter of voters used to be fairly reliable ticket-splitters. Indeed, as recently as 2004, Republican President George W. Bush won 56 percent of the North Carolina vote for reelection at the same time that Democratic Gov. Mike Easley won 56 percent of the vote for his reelection bid.

The electorate is much more polarized now. Does anyone truly believe that, say, in 2020 Roy Cooper could win reelection with 56 percent of the vote while Donald Trump won 56 percent of North Carolinians’ votes for president? Both won in 2016, of course, but their margins were either close (four points for Trump) or razor-thin (two-tenths of one percent for Cooper).

The share of voters truly up for grabs is probably in the single digits now in our state, and not much higher in most other states (although a healthy ticket-splitting contingent still exists in states such as Massachusetts and Maryland that are generally blue but seem poised to reelect their popular Republican governors by large margins).

The primary explanation, according to most analysts, is that the parties have become more ideologically standardized. Historical patterns of conservative Democrats in places like North Carolina and liberal Republicans in places like Connecticut have run their course. The two major parties have sorted themselves ideologically. Voters have followed suit.

The rise of the unaffiliated voter is not a challenge to this explanation, by the way. Joining a party and voting consistently for a party are not the same thing. Nearly a third of North Carolina voters have no partisan registration. There are more unaffiliated voters than there are registered Republicans. Still, the vast majority of these unaffiliated North Carolinians vote reliably red or reliably blue. They may not be joiners. But they have strong partisan preferences.

I have made this observation many times, and I stand by it. However, there is an ambiguity that sometimes causes confusion. To say that most voters have sorted themselves by party is not to say that there is only one kind of Republican or one kind of Democrat. The two major political parties remain broad coalitions, not the political equivalent of religious denominations.

Different analysts use different taxonomies to describe them. One longtime system, based on surveys by Gallup and other pollsters, identifies two different Republican-leaning groups, Conservatives and Libertarians, along with Progressives and Populists as Democratic groups plus a shrinking but still significant Centrist group in the middle.

Other taxonomies are more complicated. A new study called Hidden Tribes, published by the organization More in Common, has been making headlines recently. It identifies seven groups on a left-to-right scale: Progressive Activists, Traditional Liberals, Passive Liberals, Politically Disengaged, Moderates, Traditional Conservatives, and Devoted Conservatives.

Setting aside the pros and cons of each approach, the valuable part of such exercises is that they distinguish between partisan polarization and viewpoint polarization. Reliably Republican voters disagree among themselves on a variety of issues. So do voters in the Democratic coalition.

These disagreements can be passionate. But switching one’s partisan allegiance in response to such disagreements has become surprisingly rare. That’s polarization for you. It explains a lot about today’s politics. Whether the phenomenon will persist into the future is anyone’s guess.

John Hood (@JohnHoodNC) is chairman of the John Locke Foundation and appears on “NC SPIN,” broadcast statewide Fridays at 7:30 p.m. and Sundays at 12:30 p.m. on UNC-TV.