The viewership was up 34 percent from the 46.6 million people who watched the first debate between George W. Bush and Al Gore in 2000, according to Nielsen Media Research. That 2000 debate had competition from a baseball playoff game.

NBC, with 17.2 million viewers, topped the seven networks that aired the 90-minute debate, Nielsen said.

During the debate, television networks ignored Bush and Kerry campaign wishes that they not air reaction shots - and President Bush's occasionally peeved expression showed why they couldn't resist.

Cameras caught the president's irritation during some of Sen. John Kerry's responses. Kerry, for the most part, maintained a stoic expression and jotted notes.

The meticulous agreement between the Bush and Kerry camps on debate logistics called for television cameras to remain trained on the candidate speaking. None of the networks played along, arguing reactions were part of the story.

C-SPAN, as it has done before, had a split-screen image of Bush and Kerry for the entire debate.

"If you were in the audience and in the room, you got to see the reactions," said Brian Lamb, C-SPAN's chairman and chief executive. "Why shouldn't the public?"

The campaigns didn't make an issue of it. Bush was told before the debate that a camera would be focused on him for the entire 90 minutes, said Nicole Devenish, campaign communications director.

"The president is a man of deep convictions," Devenish said. "The president reacted honestly. It showed the president really believes in his convictions."

Lamb said the reaction shots can work both ways. In 2000, cameras and microphones caught Gore sighing at some of Bush's answers, and that turned some voters off.

"I don't even know if showing him being agitated was necessarily a negative," Lamb said. "It showed the way he was."

Campaign spinners were working overtime on Friday. White House communications director Dan Bartlett and Democratic vice presidential candidate John Edwards presented their sides on all three network morning shows.

NBC, meanwhile, said it made a special effort not to declare a winner or loser of Thursday's debate, after reading research that showed many voters' opinions of the debate were formed as much by punditry as by what they saw.

Unlike ABC and CBS, the network did not conduct an instant poll of viewers to determine who won or lost, said Tom Touchet, executive producer of the "Today" show.

"We gave it a lot of thought as a network news division," Touchet said. "It's important for us not to be an active part of the decision-making process, to let the facts present themselves and not to in any way, shape or form declare a winner or loser."

Nielsen ratings for the debate offered indications of a potential viewer backlash against CBS's Dan Rather, under fire for the network's discredited report on Bush's National Guard service.

For much of the country, the hit show "Survivor" preceded the debate, and it led all the networks in its time slot with 21.1 million viewers, Nielsen said. But for the debate itself, CBS had 13.5 million viewers - actually lower than for the first Bush-Gore matchup in 2000.

That indicates a significant number of viewers switched channels from CBS when the debate came on. By contrast, NBC, ABC and Fox all had more viewers for the debate than they had for the programs immediately preceding them, Nielsen said.

Still, CBS ranked second behind NBC for most debate viewers. For the half-hour of analysis after the debate, CBS slipped to third behind ABC.

The second presidential debate is scheduled for Oct. 8. Fox will not televise that debate because of baseball playoffs.