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ASHEVILLE, N.C. -- North Carolina's population has nearly doubled since 1970, fueled by an economic expansion that brought an influx of Midwesterners, Northeasterners and nonwhites and turning the state from a Republican presidential stronghold into a battleground.

Among the new residents: Carol Fentiman, 66, a Chicago native who retired with her husband to the western Carolina mountains seven years ago from California and is a Democratic Party volunteer. And Piper Phillips, 18, a college student who moved here a year ago from Ohio and who will cast her first presidential ballot this year for Barack Obama.

To explain their upcoming votes, both cited women's health care and abortion rights, civil rights for gay Americans and equal pay for women.

"I'd like to be considered an equal citizen in this country," Fentiman said.

On the strength of young voters, African-Americans and urban voters — many of them born elsewhere — Obama won North Carolina in 2008 by 14,177 votes out of 4.3 million. He was the first Democrat to prevail here since Georgia's Jimmy Carter managed a Southern sweep in 1976. Democrats chose Charlotte for their 2012 nominating convention, and polls suggest another thin margin between the president and Republican challenger Mitt Romney.

Obama's win surprised many of the state's political players.

Advantages from a younger, less native, less white, more urban electorate weren't expected to level the field for Democrats so soon, but Obama employed an extensive ground game that, four years later, still operates more than 50 field offices. Those outposts use volunteers like Fentiman to register tens of thousands of new voters like Phillips.

"Obama sped up the clock," said Ferrel Guillory, a University of North Carolina expert on Southern politics. Guillory said the winning threshold for Democrats had been 40 percent of the white vote statewide. "Obama proved you could win with 36 or 37 percent," he said.

North Carolina's growth is due to economic diversification that distinguished the state from its Southern neighbors. An agrarian and manufacturing economy dominated by tobacco, furniture and textiles gave way to banking centers in Charlotte, myriad health care enterprises and the biomedical and technology firms in the Research Triangle of Raleigh, Durham and Chapel Hill. Much of it is connected to a network of well-regarded public and private universities.

Not all the newcomers are Democrats. Eastern coastal areas that attract some retirees have been reliably Republican in recent federal elections. Mid-career professionals span the spectrum. Independents compose the largest crop of new registrants.

Many native white North Carolinians like Greenville's Lebern Rouse Jr., meanwhile, have abandoned their old Democratic loyalties as a vestige of the once "Solid South." Rouse, 65, recalled that his father "always heard that Democrats were for the small, working man and Republicans were for richer people." But, he added: "As time went by I rejected that, and so did he."

What has emerged is a genuine swing state, even if one where long-standing inconsistencies and quirks are still at play.

For decades, as Republicans won the presidential vote, North Carolinians left Democrats in charge at the Statehouse. A state that chose notable progressive governors Terry Sanford and Jim Hunt sent the firebrand conservative Jesse Helms to the U.S. Senate for 30 years.

"I guess we are just a bit schizophrenic," said Richard Vinroot, a Republican and former Charlotte mayor who lost a close governor's race to Democrat Mike Easley in 2000.

Now, as Obama brings Democratic advantages to a head at the top of the ticket, Republicans are engineering a down-ballot takeover. In 2010, the GOP captured legislative majorities in both chambers for the first time since Reconstruction. Social conservatives won a victory in May when voters easily approved a constitutional ban on same-sex marriage.

Vinroot's successor in Charlotte, Republican Pat McCrory, is favored to win an open governor's seat in November. Democratic Gov. Beverly Perdue opted not to seek a second term. The party also is set to pick up as many as four congressional seats in Democratic districts that Republican legislators redrew to GOP advantage.

Gary Pearce, a Democrat who worked for Hunt, argued that North Carolina's fundamentals haven't necessarily changed. "There have always been what I call the two tribes," he said, referring to the "progressive tradition" anchored by the universities and cities and "the more conservative, more racist strain" in the rural counties that propelled Helms. The difference, Pearce said, is that divisions have hardened.

Vinroot, the Charlotte Republican, agreed and said that reduces the pool of potential ticket splitters, voters that Vinroot described as resenting an active federal government but who "still wanted state government to do all those things."

Rufus Edmisten, a former Democratic attorney general and secretary of state, called it the "nationalization of North Carolina politics. There's just a clear distinction about which party is which, now. It's hard to find a self-described conservative who is a Democrat anymore."

Guillory, the UNC expert, said that means North Carolina elections, including Obama vs. Romney "will turn even more on the ground game, on getting your loyalists to the polls."