(CNN) -- Sen. Barack Obama has enjoyed double-digit leads in North Carolina for months, but Sen. Hillary Clinton has narrowed the gap going into the state's Democratic primary Tuesday.
Sen. Barack Obama speaks at an LED factory in Durham, North Carolina, on Monday.
Polling places in North Carolina open at 6:30 a.m. ET and will close at 7:30 p.m. ET. The voting will determine how the state party will split 115 delegates between Clinton and Obama.
A CNN poll of polls for the North Carolina race, calculated Monday, has Obama leading Clinton 50 percent to 42 percent, with 8 percent unsure.
The poll of polls is an average of three polls conducted between April 29 and May 4: Zogby, American Research Group, and Research 2000. A sampling error for the poll of polls cannot be calculated.
A Los Angeles Times/Bloomberg poll of likely North Carolina Democratic primary voters taken April 10-14 had Obama leading Clinton by 13 points, 47 percent to 34 percent, with 19 percent unsure. The poll's margin of error was plus or minus 4 percentage points.
Clinton, however, has a pretty steep hill to climb if she is to catch her rival. North Carolina's demographics are working in Obama's favor. The state's large African-American population is expected to make up 40 percent of the primary electorate, giving Obama an advantage in the state.
North Carolina also has large populations of young voters, students and upscale white voters -- groups Obama has done well with in previous primaries. Watch Obama call himself the most electable candidate »
Obama may also benefit from the support of independents, as he has done in previous primaries. Independent voters in North Carolina are allowed to vote in either the Republican or Democratic primaries. But given that Sen. John McCain has already wrapped up the Republican presidential nomination, independents may be more likely to participate in the Democratic contest.
Clinton, however, has worked hard to cut into Obama's lead. She won the endorsement of the state's popular Democratic governor, Mike Easley, and has been campaigning heavily across the state, at times making speeches on the backs of pickup trucks. Watch how Obama says he differs from Clinton »
And to nail down support from working-class and rural voters, former President Bill Clinton, the campaign's self-proclaimed "ambassador to small-town America," has been crisscrossing the state's rural back roads.
Hillary Clinton's call for a gas tax holiday has been at the heart of her message of help to working-class voters who are having difficulty making ends meet. North Carolina has been hit hard as jobs in the textile industry have gone overseas. Watch Clinton make her last pitch to North Carolina voters »
Obama -- as well as many economists -- has criticized the gas tax holiday as pandering and has called it "a classic Washington gimmick." The senator from Illinois said that if the gas tax were suspended, oil companies would be more likely to pocket the savings than to pass it on to drivers.
Clinton says she backs the tax holiday despite the "elite opinion" of economists who have widely called it an ineffective way to lower record gas prices.
"I'm not going to put my lot in with economists," Clinton told George Stephanopoulos on ABC's "This Week" on Sunday, after he asked her to name a single economist who supports her plan. "If we actually did it right, if we had a president who used all the tools of the presidency, we would design it in such a way that it would be implemented effectively." E-mail to a friend
CNN's Peter Hamby contributed to this report.