The third in a 10-part weekly series

No Republican has won the White House since 1956 without North Carolina in his column — and the state will be crucial again in the 2016 race for president, this time for GOP nominee Donald Trump.

It is highly unlikely Trump will chart a path to 270 electoral votes against Hillary Clinton if he does not lock up the Tar Heel State. But if North Carolina has earned a reputation as Republican-leaning over the past 10 presidential elections, having backed the Democratic nominee only twice, that advantage has eroded over the past decade, leaving challenging and uncertain terrain for both candidates.

Underlying the shift have been fundamental changes in the composition of the state’s population and demographics. North Carolina has in recent years seen an influx of white-collar professionals, from the Northeast in particular, as the urban centers of Charlotte and Raleigh-Durham have boomed. Once lagging the nation in its share of residents with post-secondary educations, it has now surpassed the national average.

Meanwhile, many of its rural communities have diminished, with 48 of North Carolina’s 100 counties having lost population since 2010, in areas where agriculture or manufacturing historically thrived.

“The combination of technology and offshoring have really reduced the workforce required for those industries, or they’ve reduced those industries entirely,” said Rebecca Tippett, director of Carolina Demography at UNC-Chapel Hill’s Carolina Population Center.

But “rural communities can still have significant impact,” Tippett added, “because they have an older, almost 100 percent voting [eligible] population. … When you’re talking about the younger generation, we know that it becomes a question of what percent are registered and what percent actually turn out.”

Though Hispanic and Asian communities have been on the rise in North Carolina, voter registration among these groups has lagged, often by a generation. In 2016, Latino voters will comprise just 2 percent of the electorate; this group’s political influence won’t truly be felt in the state until 2020 or even 2030, Tippett estimated.

“That’s part of the reason why North Carolina is such a tossup state, because these changes are working their way through the population but haven’t fully taken hold in the electorate yet,” she said.

Perhaps no state has more publicly grappled with its own political and cultural identity over the past year than this one -- in heated fights over voter I.D., transgender protections and discrimination laws.

A law requiring a government-issued I.D. to vote, which also would have shrunk the window for early voting, was invalidated by the 4th Circuit Court of Appeals for its "discriminatory intent.”

Clinton invoked the law as a rallying cry at a recent campaign event in Charlotte, saying: “I think it’s one of the great gifts of our democracy that we have the opportunity to choose our leaders. And brave people going back so many years have fought to preserve that right. But that right is under attack right now, and it is under attack in North Carolina of all places, a state that often set the standard for moving everybody into the future.”

"Rural communities can still have significant impact because they have an older, almost 100 percent voting [eligible] population." Rebecca Tippett, Carolina Population Center

Another law preventing transgender men and women from using bathrooms designated for the sex with which they identify, and limiting protections for sexual orientation-based discrimination, sparked a national outcry: The NCAA this week decided to relocate championship games set for North Carolina, citing “the cumulative actions taken by the state concerning civil rights protections,” and the NBA similarly moved its 2017 All-Star Game from Charlotte. Other corporations have refused to do business in the state, and some musical acts have canceled concerts.

With Republican Gov. Pat McCrory facing a re-election fight this year, Democrats hope these controversial laws will bring voters to the polls who might not be enthusiastic about the presidential race.

Clinton’s far-reaching campaign organization, which boasts 33 offices in North Carolina, is another source of optimism for Democrats.

“She’s had her staff in place, her senior team, since May,” said former Sen. Kay Hagan, a Democrat who is campaigning for Clinton. “Compare that to the Trump campaign.”

Trump’s team has no office space of its own in the state, and the Republican National Committee only this week began opening its “victory offices” in conjunction with the campaign. And Trump has only begun to answer millions of dollars’ worth of advertising by his opponent and her allies.

“The Trump people have completely missed the mark on what they need to do to put together a winning campaign in North Carolina,” said one state Republican strategist.

Clinton's "had her staff in place, her senior team, since May. Compare that to the Trump campaign." Former Sen. Kay Hagan

A powerful organization on the ground was one factor that propelled Mitt Romney to victory over President Obama in North Carolina four years ago.

“I think one of the reasons [Obama] lost is ... after the convention in Charlotte, Obama pulled out of North Carolina, which I think, in hindsight, had the campaign stayed in North Carolina, they probably could have won North Carolina, too,” said Hagan. “And I think that Hillary Clinton is now seeing the importance of North Carolina and the Electoral College votes” – 15 -- “that come with a state like North Carolina.”

Still, the RealClearPolitics polling average shows a tight race there, with Clinton maintaining an advantage of 0.8 percentage points over Trump. On average, 12 percent of North Carolinians are unsure of their preference or support a third-party option.

The outcome, Tippett predicted, will likely come down to the college-educated voters whose ranks have been growing in the state and who so far have viewed Trump with skepticism or concern.

“In a tight election with many competitive statewide races, a lot of the outcome is going to come down to suburban voters in Charlotte and Raleigh,” Tippett said. “That’s probably a college-educated professional.”

Update: Rebecca Tippett's quote about rural communities' voting tendency was modified for clarity at 12:03 p.m. Sept. 15.

Next week: Pennsylvania

Rebecca Berg is a national political reporter for RealClearPolitics. She can be reached at rberg@realclearpolitics.com.