But behind the elaborate preparations and gung-ho attitude, the television networks are heading into the night with a sense of cautious restraint -- especially when it comes to exit polls -- all too aware of the implications of a botched call.

"We don't want ever a repeat of what happened in 2000," said Phil Alongi, executive producer of NBC's special events, referring to the networks' haste in awarding Florida to Al Gore, then giving the state to George W. Bush before realizing it was too close to call.

"We learned so many lessons across the board," he said. "One of the first: Get it right."

To do so, the networks now follow strict rules that govern projections, examining not only exit poll data but actual vote tabulation and turnout information. NBC -- which keeps its decision desk isolated from the calls made by competing networks -- will only call a winner once its statisticians conclude that the chance of an error is less than 1 in 200. And no calls will be made until all the polls have closed in a state.

Extreme measures are taken to ensure that early data from the exit poll does not leak out, as it did in 2004, when the first wave of surveys showing John Kerry in the lead rocketed through cyberspace.

For much of the day, only a small group will have access to the exit poll, which is being conducted by Edison Media Research and Mitofsky International for the National Election Pool, a consortium of the networks and the Associated Press. Three members from each outlet will be sequestered in an undisclosed location in New York, where they will analyze the results of questionnaires filled out by 100,000 voters nationwide. Their cellphones and BlackBerries will be taken away until 5 p.m. ET, when they will be allowed to share the data with their newsrooms.

It's the same procedure that was used in the 2006 midterm elections and effectively prevented the release of incomplete data, much to the relief of network executives.

"Exit poll information in the hands of trained professionals is perfectly fine," said Sam Feist, CNN's political director. "Exit poll information in the hand of the general public, who may not understand what it means or stands for, can be dangerous."

That's because exit polls are designed to provide a demographic portrait of voters, not to predict the winner of a close race. The early waves of data can be especially misleading because they do not necessarily reflect an accurate sample of the electorate.