RALEIGH, N.C. — In September, a Time Magazine poll showed President George W. Bush with an 11 percent lead over Sen. John Kerry. The same week,

The Christian Science Monitor

reported a tie. Experts warn potential voters that polling is not an exact science.

Sen. John Kerry came out of Friday's debate with a slight lead according to one poll, but experts say it is important to remember polls are just a snapshot.

"Most polling is fairly accurate. The trouble starts when you think that polling is making a prediction," said Michael Cobb, political science professor for North Carolina State University.

Cobb said polling methods vary widely. He had problems with a recent Gallup presidential poll.

"Their sample was comprised of about 7 to 8 percent more Republicans than Democrats and that would be fine if that was what America looked like, but it doesn't," he said.

Cobb also said opinions people give right after debates do not always last.

"That can change over a couple of days too as the pundits get their hands on the debate and explain what they think happened and that can often change people's perception of what they saw," he said.

Cobb said polls will be more accurate the closer voters get to Election Day.

"People are more certain whether they can going to vote and they are more certain about who they are going to vote for," he said.

Neither Republican nor Democrat officials put full faith in polls they don't control.

"Polling are not an exact science, but what they do do is give you a roadmap of where your campaign needs to go," said Republican media consultant Marc Rotterman said.

"I wouldn't put a lot of stock in any one single poll, but I would put some stock in the way the polls are trending," said Scott Falmlen, of the state Democratic Party.

Cobb said if the recent surge in new voter registration favors one party over another, that may not be reflected in polls because many of the new voters are not getting phone calls yet.

Those who rely solely on cell phones to stay in touch are not in touch where presidential polling is concerned. Pollsters cannot call cell phone numbers.

The U.S. Census Bureau said about 5 percent of households rely only on cell phones. Among young adults, though, the number is nearly 15 percent. However, pollsters claim those people often do not vote anyway and regardless, the number is too small to affect research.