Hillary Clinton's recent surge in the polls is being fueled in part by a demographic that President Obama lost handily four years ago — white, college-educated voters.

"In over a half-century, no Democratic presidential candidate has carried white voters with a college degree," said Michelle Diggles, a senior political analyst with the center-left think tank Third Way, who described the split between the white working class and whites with a college degree as "the most underreported story of this year."

GOP nominee Donald Trump is hoping that white working-class voters can fuel his own victory. But his climb becomes doubly harder as he is far behind Clinton in the demographic bloc that is usually reliably Republican.

In the last presidential election, Barack Obama lost the college-educated white voters by 14 points. But now Clinton is winning this same group by about 8.7 points, according to an average of the most recent NBC/Wall Street Journal, CNN/ORC and ABC/Washington Post polls.

"In the past, many college graduates, white people that were business managers or had various kinds of middle-class jobs, would vote Republican — and that group may be taking a second look at the Democratic Party," said Bill Frey, a demographer at the Brookings Institution.

NPR only had access to exit polls dating to 1988, but with the help of the Pew Research Center, we were able to identify the education/class divide and explore the Republican dominance over time.

Why are we seeing a shift now?

"It seems that Donald Trump is a uniquely polarizing figure amongst white voters," Diggles observed. "There are a lot of voters who are concerned that Donald Trump is ... just so outside of the mainstream and so outside the American political culture that they can't fathom it."

She pointed to Trump's close ties to Russian President Vladimir Putin, his "anti-democratic" rhetoric, and his threats to the freedom of the press.

The outspoken billionaire's immigration policy — which includes mass deportations and plans to build a wall between Mexico and the U.S. border — also does not seem to resonate well with some well-educated voters.

Trump's tone and antics, particularly in the week following the Democratic National Convention — which included a fight with a Muslim American military family, a reluctant endorsement of House Speaker Paul Ryan and a strange response to sexual harassment — did not help his case either.

GOP strategist Lisa Camooso Miller said she is not surprised college-educated voters seem to be tilting toward Clinton, given the "tone" of the two conventions — the DNC as one of hope but the Republican National Convention as one of fear.

"I think people that are college educated have a general understanding that America is the melting pot ... and that's what makes this country great," she said. "I think that the more [Trump] identifies and specifically singles out various segments of the population, I think that turns people off."

Camooso Miller also observed that college-educated voters probably prefer Clinton's stability and predictability, regardless of whether they agree with her specific policy proposals.

Frey agreed, arguing that the overall message of the GOP convention depicted an impending era of "doom and gloom," targeting Americans who are suffering in the current economy; but he said college-educated voters are more likely to see their jobs as part of a global economy.

Frey also believes that for some college-educated voters (who might traditionally vote Republican for economic reasons), the overall vision and identity of the country has become more pivotal to their vote than the economy.

"[Trump's candidacy] has become not so much an intraparty battle as it has become a battle about what is America," said Diggles, explaining why we have seen a spate of recent defections of high-profile, highly educated Republicans.

What does this mean for November?

If the polls are accurate, having a college education seems to be a key indicator of how white voters will cast their ballot on Election Day.

Using census data, NPR ranked all 50 states according to the share of the white (non-Hispanic) population, age 25+, with a bachelor's degree or higher.

This helps understand which states may be at play this November and why.

For example, there are a few states on polar opposite ends of the education spectrum:

In recent election cycles, blue-collar white voters have voted consistently Republican; Trump is hoping to do better than Mitt Romney or John McCain did with this group in 2012 and 2008, respectively. And in the Buckeye State, it's a gamble that might pay off.

"I certainly think Ohio is a state where there's a good possibility that the noncollege whites could bring a victory to Donald Trump ... if they up their turnout," said Frey. He pointed out that many working-class voters feel like they've been left behind in a modern economy, and so they're "buying" any message Trump sells them.

In Pennsylvania, another critical battleground state, the white demographics aren't much better for Clinton (29.41 percent), but there's a larger African-American and Latino population to offset the white population.

An era of "Clinton Republicans"?

It's hard to say whether this realignment of college-educated white voters is a short-term Trump side effect or the beginning of a new political label — so-called Clinton Republicans.

Trump is certainly a "change" candidate, as evidenced by the coalition he built during the GOP primary.

But that change hasn't necessarily appealed to highly educated voters. Last week, the oldest college Republican group in the country, the Harvard Republican Club, said it was "ashamed" of Trump. It announced it will not be endorsing the GOP presidential nominee — a first in the group's 128-year history.

But Frey questions whether that shift away from Trump will last long-term.

"I think this time, whoever votes against Donald Trump is not someone who's necessarily gonna stay with the Democratic Party for year after year after year in the future," said Frey. "It's probably more a vote against the brand of candidate that Donald Trump represents than maybe a vote against the Republican Party."

For reasons like that, Camooso Miller remains optimistic about her party's future.

"I think that 2016 is an example year, and is not necessarily the norm," she said. "I do not think this is a trend that will grow."

The GOP strategist pointed to other Republican leaders, such as House Speaker Paul Ryan, who who could help re-energize and re-engage this college-educated white voting demographic in the future.

Democrats' millennial advantage

Still, the very people who make up the college-educated white demographic are not necessarily the same people who voted eight years ago. The composition has fundamentally changed.

Millennials, the youngest generation of voters, have grown up and now rival baby boomers as a political force — with an estimated 69.2 million eligible voters, according to data from the Pew Research Center. Millennials lean left and are the most educated demographic to date, and they are an increasingly large share of the overall white college-educated bloc.

Plus, Diggles insisted that in all of the focus groups she has conducted, she consistently sees a difference between older and younger white men, regardless of their level of education.

Polling shows that white millennials are skeptical of a Trump presidency. So as those voters get older, unless they change their political attitudes drastically, the Democratic Party may have an inherent advantage in future elections.

The education/race cleavages explain why the Trump campaign is spending so much time and effort in Ohio and Pennsylvania — Rust Belt states where the white population is less educated than the country as a whole. Because while Clinton may have a single-digit edge with educated voters, Trump has a double-digitadvantage with white working-class voters. And in these states, the GOP nominee has more room to grow because there's a larger pool of voters he can potentially energize.

As NPR has reported previously, noncollege white voters, especially men, are one of the most consistently Republican voting blocs — so-called Reagan Democrats.

"They think that Donald Trump isn't afraid to speak his mind, and he speaks in a language that represents them and their anger," said Diggles, who points out that in focus groups she often hears from white men nostalgic about the past and frustrated that their economic fortunes aren't as good as their fathers' or grandfathers'.

Obama lost white blue-collar voters by 25 points, according to 2012 exit polls. But that still wasn't enough to derail his re-election.

To win this year, Trump will need to win white working-class voters by even bigger margins. Polling shows he is currently doing about as well as Romney did, but the hiccup for him is that white working-class voters are a shrinking share of the electorate.

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