Raleigh, N.C. — Sometime between December 2011 and Election Day, Wake County quietly marked an electoral milestone that may determine the outcome of elections for years to come. 

The number of voters registered as "unaffiliated" surpassed the number of registered Republicans in the county home to the state's seat of government.

 In 2000, unaffiliated voters outnumbered one of the two major parties in only two relatively small counties. They outnumbered Democrats in Avery and Mitchell counties.

Today, there are more unaffiliated voters than Democrats in nine North Carolina counties, while unaffiliated voters outnumber Republicans in 30 counties, including voter-rich urban areas like Wake, Cumberland, Durham and Mecklenburg.

In two more counties, Currituck and Watauga, unaffiliated voters outnumber both Democrats and Republicans.

"If I was a leader in either party, that would be a real sobering reality for me to digest and to try to cope with," said Tom Fetzer, a political consultant and former state Republican Party chairman. "How do I make my party relevant and inviting?"

North Carolina Republicans are celebrating big wins in this year's gubernatorial, legislative and congressional elections. Compared to national trends, North Carolina is a bright spot on the national horizon for the GOP.

But Fetzer cautions that, four years ago, it was the Democrats celebrating big wins.

"Both parties have a challenge to remain relevant, because the vast majority of people are choosing to join neither," Fetzer said.

Statewide, unaffiliated voters are still the third-largest group behind Democrats and Republicans. But political observers say the boom in unaffiliated registration is a trend that doesn't appear to be abating.

"It's hard to know without survey data who these people are," said Ferrel Guillory, a journalism professor and director of the Program on Public Life at the University of North Carolina at Chapel Hill. "But it (the rise in unaffiliated voters) coincides with the tremendous population growth the state has had."

Those coming to North Carolina may be arriving from states where people don't declare their party affiliations or where the messages of the major parties don't sync with the messages put out by the parties in North Carolina. Anecdotal evidence suggests a significant portion of young voters seem to be choosing not to sign up with one party or another when they come of age. 

Also important: A fair number of unaffiliated voters are behaving like loyal Republicans or Democrats but have chosen not to declare themselves for one reason or another.

"It's easier to be an unaffiliated voter now, in the sense that you can still vote in primaries," Guillory said. "You used to have to be registered in party or the other to vote in a primary."

All of which is not to discount the power or importance of parties. Party affiliation is still a powerful predictor of how someone will behave when they go to vote. 

Out of 4.5 million votes cast in the state this year, 2.5 million were straight-party tickets, an increase from the number of straight-party ballots cast four years ago.

So North Carolina's electorate includes both party faithful as well as ticket-splitters. 

Exactly how many voters split their ticket in the state is unclear. But 171,000 more voters backed Pat McCrory, the Republican candidate for governor, than voted for Mitt Romney, the Republican presidential nominee.

"There's probably a larger persuadable universe of voters than there was 20 years ago," said Tom Jenson, a pollster with the Democratic-leaning Public Policy Polling.

Democrats, he said, used to be able to win elections just by turning out their base. But unaffiliated North Carolina voters backed Republicans 2-1 at the polls, he said, a trend that helped bring about Republican legislative majorities in 2010 and 2012 and put McCrory in office. As Democrats look to recover from this year's drubbing, he said, reaching unaffiliated voters has to be part of the plan.

"It's particularly incumbent upon Democrats to come up with a message that's attractive to these unaffiliateds," he said.

As for Republicans, the growing number of unaffiliated voters should temper their enthusiasm.

"Unaffiliated voters are not voting Republican because they love Republicans," he said. Unaffiliated voters appear to have been punishing state-level Democrats, particularly Gov. Bev Perdue, for what they perceived as poor performance.

"If unaffiliated voters loved Republicans, they'd be Republicans. The easiest way for the Republican Party to blow their advantage is to take this as too much of a mandate."