Hours before voting was done Tuesday, exit polls had revealed McCain was headed for a surprisingly big victory over GOP frontrunner George W. Bush.

The three cable news networks declared McCain the winner at 7 p.m. EST, when most -- although not all -- of New Hampshire's polls closed.

Fox News Channel's Brit Hume had reported at 6 p.m. that "all signs point to a very good night for John McCain." Much of the next hour included discussion on the implications of a big McCain victory.

"To do otherwise would have taken us completely off what we knew to be the news," Hume said Wednesday.

Early victory projections were a big issue in the 1980s, when West Coast politicians worried that network calls on a presidential race would keep voters at home.

Research on whether this was true has been inconclusive, said Tom Rosensteil, director of the Project for Excellence in Journalism. But networks have generally waited in recent elections to avoid alienating voters, he said.

With two new cable news networks this presidential election and more refined exit polling, there's a greater temptation to break ranks, said Kathleen Jamieson, dean of the Annenberg School for Public Communication at the University of Pennsylvania.

Instead of a competition among news networks on who could call the race first, "we got into a race of who could insinuate first," Jamieson said.

On the "CBS Evening News" at 6:30 p.m., Dan Rather said there were "early indications of possible surprises" in both parties. Correspondent Bob Schieffer said exit polls concluded New Hampshire Republicans gave McCain an "astonishing" 70 percent favorability rating.

David Bloom said on NBC's "Nightly News" that "the McCain camp is brimming with confidence tonight, and Bush aides appear resigned to defeat."

ABC waited until 8 p.m., when all New Hampshire polls had closed, to declare McCain the victor. But Peter Jennings reported 90 minutes earlier that it appeared to be a good day for McCain.

Rosensteil said that television commentators "pushed the semantic envelope more last night than I have seen in a long time."

"We would argue that it's not semantic," ABC spokeswoman Eileen Murphy said. "You're not projecting a winner."

CNN's 7 p.m. declaration made for one awkward moment: a half-hour later, Judy Woodruff noted on the air that polls hadn't closed everywhere in New Hampshire and that voters should exercise their rights.

Before 7 p.m., CNN political director Tom Hannon said he emphasized to correspondents not to let what they knew from exit polls seep into their reporting.

"The risk of influencing, potentially, the outcome of an election is a weighty responsibility, so we kind of play it straight," Hannon said. "I recognize that it's a difficult issue. I'm not trying to imply any criticism of the other networks."

Hume said Fox tries to strike a balance.

"You don't want it to be a situation where the media and all the players know what the score is and the spectators don't," he said. "There's nothing more journalistically suspect to me than a bunch of journalists working with a head full of knowledge and not telling the audience."