The primary, offering 115 national convention delegates, comes two weeks after Pennsylvania gave the former first lady the win she needed to stay in the race. But Obama is favored to win North Carolina, the largest prize among the contests remaining.
"My crystal ball wasn't working well last year, and I certainly would not have anticipated this," said state Democratic Party chairman Jerry Meek. "But, in retrospect, having a May primary was a tremendously astute decision."
Voters, especially new ones, have taken note.
More than 165,000 people have registered to vote in North Carolina in the first three months of the year, a nearly threefold increase from the same period in 2004. Election officials expect a record turnout May 6 - about half of the more than 5.7 million registered voters, compared with past turnouts ranging from 16 percent to 31 percent.
Another wild card: A new law allows unregistered voters to sign up and vote on the same day through May 3. Both campaigns have launched efforts to turn out those voters, and the polling sites have been flooded since they opened last week.
As of Thursday morning, more than 81,000 "one-stop" ballots had been cast - about eight times higher than during the 2006 primary, according to the state Board of Elections. An additional 8,700 absentee ballots have been collected, officials said.
Voter registration is up overall, but the biggest boost has been among blacks.
More than 45,000 black voters have registered in the first three months of 2008, compared with just over 11,000 in the same period four years ago. Blacks make up more than 20 percent of the state's registered voters, according to Board of Elections data.
Those numbers bode well for Obama, who has won strong black support throughout the primaries.
There are other signs Clinton will have a hard time achieving victory in North Carolina.
Neither of the state's top two Democrats, outgoing Gov. Mike Easley and former White House hopeful John Edwards, have endorsed a candidate. Among superdelegates who have made their choice known, Obama has a 6-1 edge. The 10 remaining superdelegates, including Meek, are uncommitted.
The two Democratic candidates vying to replace Easley, who is barred by law from seeking a third consecutive term, are not only backing Obama but have made their support for him a feature of their campaigns.
State Treasurer Richard Moore has run radio ads on stations popular with black listeners noting he "was the first Democrat running for governor to endorse Barack Obama for president." His rival, Lt. Gov. Beverly Perdue, has sent mailers to likely black voters with a photo of her with Obama.
State Republican party officials have made the gubernatorial candidates' connection to Obama the focus of a TV ad scheduled to begin airing Monday that includes footage of Obama's controversial former pastor and calls the Democratic presidential hopeful "too extreme for North Carolina." On Wednesday, Sen. John McCain, the GOP's certain presidential nominee, called the ad "offensive" and asked party officials not to air it, but they refused.
Tar Heel politics are often both unpredictable and contradictory.
The state elected the populist Edwards to serve alongside arch conservative Jesse Helms in the Senate. It has not voted for a Democrat for president since 1976, when Georgia Gov. Jimmy Carter swept most of the South, but it has elected a Democratic majority to the state Senate for more than 100 years.
"People in North Carolina tend to look at individuals and offices distinctly and make the decision based on the person and the office," said Elon University pollster Hunter Bacot. "We have such a large number of independents. And they are true independents - they split ballots."
North Carolina has roughly 9 million people, making it the nation's 10th largest state. It is home to the Marine Corps' Camp Lejeune and the Army's Fort Bragg, two massive installations whose troops have suffered heavy losses in Iraq and Afghanistan.
What's left of a once vibrant manufacturing and textile industry is in tatters. Many voters blame the North American Free Trade Agreement, agreed to under President Clinton, for the decline and the thousands of job losses that followed.
The state's largest city, Charlotte, has become an international financial center as home of Bank of America Corp. and Wachovia Corp., the nation's leading retail and consumer banks.
It's high-tech economy, led by the many companies with facilities based at Research Triangle Park outside Raleigh, have withstood the national economic downturn. Home values have not suffered the same widespread decline as in other states, and North Carolina's income tax revenues remain strong compared with others.
Both Clinton and Obama started campaigning in the state long before this week's Pennsylvania primary. Clinton debuted quirky TV ads asking voters to submit questions, to which she responded in conversational spots. Obama has blanketed the state with his own ads.
Some political observers say Clinton needs to win North Carolina, the last big stop on the road to the August convention in Denver, to convince unaligned superdelegates that momentum has swung in her favor. Superdelegates are elected leaders and party officials who can vote for any candidate. That, they said, is her only chance to overcome Obama.
"She's got to build momentum - serious momentum - in order to make that argument," said Jeff Link, a Democratic strategist who advised former Iowa Gov. Tom Vilsack's brief presidential run.
"She has to have a winning streak."
