Hillary Clinton's North Carolina Firewall vs. Donald Trump

RALEIGH, N.C. -- Tim Kaine was in Jacksonville on Monday. Vice President Joe Biden swooped into Charlotte on Tuesday. President Barack Obama drew thousands of University of North Carolina students on Wednesday. Hillary Clinton returned Thursday for an evening rally in the state capital with Sen. Bernie Sanders and singer Pharrell Williams. On Friday, Obama was due back for a second time this week, making two more stops. And Saturday is Chelsea Clinton's turn in the Tar Heel State.

There's a reason North Carolina is attracting such an enormous amount of sustained attention from Democrats during the final throes of the 2016 presidential race: It's become the Clinton firewall.

Carrying 15 electoral votes, the state is less valuable than the perennial White House battlegrounds of Florida and Ohio. But there's a cold hard truth embedded in the electoral math for Republican nominee Donald Trump. Clinton can lose Florida and even drop Ohio, and still wrangle the 270 electoral votes necessary to clinch the presidency. All she needs to do is convert North Carolina to a Tar Heel-hued blue, and it's lights out for Trump.

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"If Hillary wins North Carolina, she wins," Obama stated plainly during a Chapel Hill rally on Wednesday. "And that means when I said, 'The fate of the republic rests on you,' I wasn't joking."

The state of the state's polling has been paradoxical.

In the last week, different surveys have found Trump with as high a lead as 7 points and Clinton up by as many as 3 points. But political officials on both sides here are anticipating a finish that's even tighter.

"It's going to be very close," says Patsy Keever, chairwoman of the North Carolina Democratic Party. "And the pressure is on."

North Carolina solidified its battleground status over the past two presidential cycles. In 2008, Obama carried it over Sen. John McCain by 13,692 votes, or just "two votes per precinct," as the president and first lady Michelle Obama have reminded audiences. In 2012, it was just one of two states to swing back to the Republican column, with Mitt Romney outpacing the president by 97,465 votes, good enough for a 2-point win.

But this year, the state has become the center of the political map in the waning days of an increasingly competitive election, in which Trump is nipping at Clinton's heels across the country but has yet to put her away here. It's been 60 years since a Republican nominee for president has lost North Carolina and won the White House.

At this late moment though, the numbers that matter most are the tallies for early voting, which ends on Saturday at 1 p.m.

More than 2.6 million ballots have already been cast, with Democrats holding a 10-point edge on early returns. But Republicans are 12.5 percent ahead of their early voting pace from four years ago, when they overcame their initial deficit on Election Day to win.

An undeniable concern for Democrats is lagging turnout among African-Americans. Their vote is down about 11 percent from their same-day totals in 2012, according to Catawba College professor Michael Bitzer, who is tracking the numbers on his blog, Old North State Politics.

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This is why the Clinton campaign has dispatched Obama to the state for three stops in the last three days.

"Don't just sit there and complain. Don't just sit there in the barber shop and the beauty shop, watching the Tar Heels and say, 'Ah, ya know, politics is all messed up, but what's the score?' No, no, no! You can watch the game after you vote," an impassioned Obama told the crowd in Chapel Hill on Wednesday.

Deborah Gilmore, a 66-year-old African-American woman from Chapel Hill, is supporting Clinton, but says it's understandable that black turnout would slide somewhat without an African-American leading the ticket. Ahead of Obama's rally for Clinton on the University of North Carolina campus, she chose to purchase an Obama hat over Clinton paraphernalia.

"I'm gonna miss him. I love seeing him on TV. I love seeing him anywhere. I try not to miss any of his speeches, any time," she says. "It'll help her."

Another variable is the surge in independents turning in early ballots.

"Unaffiliated voters are 44 percent ahead of their 2012 same-day totals," Bitzer says. "I think this is the true wild card in this election and have no idea how to read it."

The Trump campaign is keenly aware of the importance of North Carolina to its path as well. The GOP nominee made two stops in the state on Thursday, including one in Selma that was dedicated to military and law enforcement figures.

"They're so much more brave than me," Trump said, standing before a slate of veterans onstage behind him. "I'm brave in other ways, I'm financially brave. Big deal, right? These are real brave."

But Trump also stayed focused on skewering Clinton's credibility, highlighting the continuing questions and review regarding her use of a private email server.

"What's going on is a disgrace. We know now with almost 100 percent confidence that at least five foreign intelligence services breached the Clinton server and she tried to destroy the evidence by deleting the emails after -- not before, that was bad -- after receiving a United States congressional subpoena," Trump said, appearing to reference a source-based Fox News report and repeating a nuanced claim about Clinton's deleted emails.

Among the Trump-supporting crowd of 15,000, the bitter antipathy for Clinton was nearly universal.

"I don't want a criminal running my country. Sorry, it's harsh," says Alice Batten, a Trump supporter from Smithfield.

"If more is exposed this week, I'm hoping that the Clinton supporters will just stay home and be disgusted," says Joan Hall, of Cary.

"What has she done? F---ing lie, cheat and steal just like her husband did," says Goldsboro resident Andrew Young.

The tension engendered by the two polarizing candidates was felt even in a routine interview with Keever, the head of the state Democratic Party.

When U.S. News asked Keever inside the party's Raleigh headquarters how she thought the email controversy would impact turnout for Clinton, an aide interrupted to compare the Trump campaign's tactics to an approach often attributed to Nazi Germany.

"Are you familiar with the concept of 'The Big Lie'? It was a Hitler propaganda technique where you take your biggest weakness and you tell a lie so outrageous that it makes people believe the opposite of what is true," says Dave Miranda, the state party's communications director, who sat in on the interview.

"It's a situation where Republicans and the Trump campaign are using you in the media to float these ideas and muddy the waters and make these false equivalencies. I'd like you guys to do a better job."

Keever assessed that Democrats had moved on from the email saga to pick the most qualified person to be commander in chief.

"We're OK with it. It's done. We've gotten over it. We don't like it necessarily. It could've been done better, but it's not going to make us any less supportive of Secretary Clinton," she says.

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For the first time in modern history, Democrats have a shot at simultaneously sweeping the state's top three races: for president, governor and U.S. Senate. It's a feat Keever says would qualify North Carolina as a blue state, and a goal that national Democrats see as tantalizingly within reach.

The Trump campaign will continue a vigorous push against that trend with rallies throughout the weekend. On Friday, GOP running mate Mike Pence was slated to hit Greenville. Trump himself will be in Wilmington on Saturday and in Raleigh again Monday, on election eve.

Armed with a stable of high-profile and celebrity surrogates, the Clinton campaign is dispatching Jon Bon Jovi to hold a "get out the vote" concert in Charlotte on Sunday night.

David Catanese is senior politics writer for U.S. News & World Report and founder of the blog The Run 2016. You can follow him on Twitter and send him feedback at dcatanese@usnews.com.