What one swing state can teach us about political polarization in America

It’s no secret that city-dwellers tend to vote for Democrats.

This map shows how precincts in selected cities voted in 2008 — the last presidential election without an incumbent. In most cities, the urban core appears bright blue, and the surrounding rural areas lean more Republican. There are notable exceptions, including North Dakota’s red cities and left-leaning rural Massachusetts.

Precincts — which can include a few hundred to a few thousand voters — make it easier to spot this urban-vs.-rural disparity. These detailed neighborhood by neighborhood results make it clear how racial and socioeconomic differences play out at the ballot box.

For a window into how this polarization is affecting this year’s election, just look at North Carolina. It’s one of the most coveted battlegrounds in the country — RealClearPolitics puts Donald Trump up by just 0.8 points — and it’s facing a number of other contentious electoral battles. Republican Gov. Pat McCrory, a supporter of the highly controversial law requiring transgender individuals to use the bathroom of their birth gender, is in a tight reelection battle. So is Sen. Richard Burr, a Republican with a narrow lead in his reelection contest, according to recent polling; his race could determine which party controls the Senate. And that’s not to mention the controversy surrounding the recently struck down voter ID laws.

The number of Democrats and Republicans registered to vote in the state has barely budged since 2008 — decreasing by 5 percent and increasing by 3 percent respectively — but the number of independents has increased by nearly half.

[ The biggest Pinocchios of Election 2016]

Polls indicate there will be shifts in support from demographic groups, with highly educated whites moving toward Hillary Clinton and less-educated and working-class whites moving toward Trump. Between these two factors, there’s a good deal of uncertainty surrounding the election’s outcome.

The 2012 election in North Carolina, which had results similar to 2008, provides a baseline for thinking about what could happen Tuesday.

Trump’s weakness with women could diminish the racial divide

Trump’s weakness among white college-educated women, a traditionally right-leaning group, may make white and minority voting patterns look more similar than in past elections.

In 2012, precincts in majority nonwhite areas were far more likely to support Barack Obama than white-majority precincts. Statewide, the nonwhite precincts favored Obama by more than 427,000 votes, while the white precincts favored Mitt Romney by 519,000. Romney narrowly carried the state.

This demographic split has been so stark that the borders between white and minority neighborhoods can often be traced almost perfectly by the line between red and blue precincts. One such place is Charlotte.

Charlotte is the region’s center for business, banking and NASCAR. Since 2000, Mecklenburg County, in which Charlotte sits, saw the state’s largest shift to presidential Democrats.

[ Rural strategy takes Trump to very red places in final days]

Meanwhile, every neighboring county shifted Republican. Although Republicans won the area in all of the last four presidential races, the margins have shrunk under the influence of Democrats in its urban, minority-dense core.

It is less clear which candidate many of these white precincts will support in 2016. Around Charlotte, many of these Republican-leaning, white precincts are also highly educated. And with white college-educated women moving decisively toward Clinton (they favored Romney by six points, but polls say they will favor Clinton by 27), the Republican edge in these precincts — and therefore the racial divide — could diminish.

Income could fade as a polarizing factor

Another open question is how voting patterns will change among high- and low-income voters.

White working-class voters are moving toward the Republican Party, which has traditionally had a strong base of higher-income support, while highly educated whites, who tend to earn more money, are considering a vote for Democrats. With minority voters, who are lower-income on average, staying solidly Democratic, income could become a less-divisive factor than race or education in the election.

In the past, the income divide has been stark. Among the North Carolina precincts where the typical income is below $50,000, Obama won by 124,000 votes. The other precincts went decisively for Romney, giving him 216,000 more votes than Obama.

[ Clinton up in Post-ABC News tracking poll]

The Raleigh-Durham area, home to three major universities, the Research Triangle and the state government, has grown into the state’s stronghold for Democrats. The party’s presidential margins of victory have shot up since 2000 to be the widest in the state, with Wake County, home to Raleigh, voting for the nationwide winner in each of the past four elections.

Here, Democratic-leaning precincts are found in college-educated and lower- and middle-income neighborhoods, while Republican voters still win across the richer exurbs.

The educational divide could become starker

While the educational divide may widen this cycle, it was subtle in 2012. In approximately 2,000 precincts where fewer than a quarter of adults are college graduates, Romney was favored by 18,000 votes. And in the other 1,000 precincts, Romney was favored by over 74,000 votes. So while the more-educated were more likely to vote for Romney, it wasn’t by much. (It’s important to note though, those figures are for all voters, not just white voters, who are experiencing the vote pattern shift).

[ Can an anti-Trump surge of voters sway Texas?]

The Greensboro area, which is home to people with a mix of educational levels, will test whether 2016’s unusual political currents will disrupt party loyalties. While dotted with colleges, universities and health-care centers, Greensboro, Winston-Salem and High Point still have strong links to manufacturing, especially the furniture and textile industries hard hit by the recession and the forces of global trade. It’s an area that’s voted Republican since 2000, though Obama narrowly won in 2008. But with highly educated white areas leaning Republican in 2012 and Clinton looking strong within that group, the map may change.

How will all this new polarization affect election night results? Early voting is starting to provide hints. North Carolina’s early voters so far are whiter, older and more independent compared with all early voters in 2008 and 2012, but the group is still largely Democratic, according to state records. A New York Times Upshot projection puts the state’s early voters as +10 Clinton, and the state overall as +6 in her favor.

This growing division by educational level has the potential not only to affect results but also to reshape voting patterns along racial and income lines. While all eyes may be on the bottom line on Tuesday with the race between Clinton and Trump rapidly tightening, these new alliances could have implications for election cycles to come.