US television networks face a new challenge in covering this year's excruciatingly close presidential election: prevent closely guarded exit poll results from leaking onto Twitter, Facebook and other social media platforms.
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Americans say why they're voting (and why not) and who they're voting for.
The major TV news networks agreed to shield early exit poll data suggesting who is leading in a state until the state's polls close. That means no tweeting exit polls, posting on Facebook, or re-tweeting figures reported by others.
"We will not either project or characterise a race until all the polls are scheduled to have closed in that state," said Sheldon Gawiser, director of elections for NBC News.
Election officials worry that leaks could discourage people from voting if they think the race in their state is already decided, depressing the vote count and distorting the results. In 1985, Congress extracted a promise from the major TV networks to refrain from using exit polls to project a winner in a particular state, or to characterise who is leading, while voting continues in that area.
The closeness of this year's election between President Barack Obama and Republican challenger Mitt Romney has focused attention on key battleground states — such as Ohio, Virginia and Florida — and what their exit polls might signal about who will win the White House.
It has resurrected memories of the disputed 2000 election between Republican George W. Bush and Democrat Al Gore — some media outlets projected a Gore victory in Florida while polls in the western part of the state remained open. The networks later pulled back, leaving doubt about who won and leading to a month of recounts and court battles.
If early results become public, "it can be a real problem," said Jeff Berkowitz, a Republican strategist who runs Berkowitz Public Affairs. "For somebody who's got seven things on their list to do that day, and if they're already being told the election is over, are they really going to prioritise voting over the other six?"
Exit poll data is collected by New Jersey-based Edison Media Research on behalf of the National Election Pool, a consortium of Walt Disney's ABC, News Corp's Fox, Time Warner's CNN, Comcast's NBC, CBS's CBS and the Associated Press. The media companies use the findings to help them call results in each state, and to inform post-election analysis.
Reuters is not a member of the consortium and collects exit data with market research firm Ipsos. The news organisation will not share any exit data before polls close, a Thomson Reuters spokeswoman said.
Smaller news outlets and internet blogs are not bound by the commitment made by members of the National Election Pool, and could post any exit poll numbers they get their hands on.
In 2004, for example, The Drudge Report posted early results that favoured John Kerry. US stocks dipped, and Kerry eventually lost the race, highlighting that early and incomplete results can prove wrong. A representative for The Drudge Report could not immediately be reached by email.
There is no evidence that exit poll results influence voters, but the rise of social media means any leaked data could spread like wildfire.
After leaks in past elections, the big TV networks have taken steps to keep a tighter lid on information. While some findings previously were available as early as 1pm US Eastern time, news staff are not to be given an initial look until 5pm — still two hours before the earliest poll closings.
Following a template used in the last three elections, six analysts — one from each news organisation in the National Election Pool — will be locked in a "quarantine room" from 11am to 5pm US Eastern time on Tuesday with no phone or email access, Gawiser said. They will conduct preliminary analysis of the data before it is released to staff at the news outlets.
"They cannot talk to us. We don't know anything about it. We can't see any of these data until five o'clock," Gawiser said.
These kinds of restrictions helped keep exit data under wraps in 2008, when Obama defeated John McCain. The race also was not as close as in the two previous elections, or indeed this year's vote, reducing demand for early information.
This year, the tight race and prevalence of social media increases the risk that data will spread quickly if it leaks, said Tom Rosenstiel, director of the Pew Research Centre's Project for Excellence in Journalism.
"If that were to happen today, with internet penetration and the speed of social media, that [data] would be known pretty widely," he said.