But Fox said the early rating is up 2 percent from the average of the past five years.
A ratings point represents 1,096,000 households, or 1 percent of the nation's estimated 109.6 million TV homes. The share is the percentage of in-use televisions tuned to a given show, meaning 63 percent of TVs that were on were tuned to the game.
More precise measurements of the entire country were to be available later Monday.
Nielsen did not have immediate estimates on how many people watched the game, but it seems on a par with the last two years. Nielsen said 89.8 million people watched last year, and 88.6 million in 2003.
The host city -- Jacksonville, Fla. -- drew the highest rating of any major city, trailed by Philadelphia. Boston was third.
The Patriots won their third Super Bowl in four years Sunday, 24-21 over the Philadelphia Eagles, and now they are challenging history.
It was their ninth straight postseason victory, equaling Vince Lombardi's Green Bay Packers. It was coach Bill Belichick's 10th playoff victory in 11 games, one better than the great Lombardi. And it matched Dallas' run of three championships in four years in the early 1990s.
But the Patriots themselves are still reluctant to use the word dynasty, CBS News Correspondent Steve Futterman reports.
"You know, I will leave the comparisons and historical perspectives to everybody else," Belichick said.
"We've never really self-proclaimed ourselves anything," said Tom Brady, who is 9-0 in the playoffs. "If you guys say we're great, we'll accept the compliment."
This one wasn't overpowering, and at times it was downright ugly. But not even Belichick seemed to care about that.
"To me this trophy belongs to these players," Belichick said. "They met all comers this year, a very challenging year. We're thrilled to win. These players played great all year, their best in the big games and they deserve it, they really deserve it."
With MVP Deion Branch tying a Super Bowl record for receptions with 11, Brady efficiently running the offense and Rodney Harrison sparking a smothering defense, the Patriots (17-2) didn't need a last-second field goal from Adam Vinatieri this time.
But his kick - a 22-yarder with 8:40 left - provided the points that made the difference.
This time, the Patriots sealed it with a stop.
Philadelphia (15-4) got the ball back at its 4 with 46 seconds remaining. It was hardly enough time and far too much territory to cover against such a formidable foe.
Harrison got his second interception with 9 seconds remaining to end it.
Playing before a sea of mostly green jerseys in the crowd of 78,125, the Patriots ended Philadelphia's chance of heading north with its first pro sports title since 1983. Indeed, it's been 45 years since the Eagles won the NFL crown. And even though they made it to the Super Bowl for the first time since 1981 - after three straight conference championship flops - their sparkling season still ended in disappointment.
"We were too sloppy to win," receiver Terrell Owens said. "It was great to get back, but we made too many mistakes. We could have won and that hurts."
Corey Dillon, a newcomer to the championship game, scored the go-ahead points on a 2-yard run early in the fourth period. And when Branch wasn't catching passes, the Patriots flaunted their versatility by again using linebacker Mike Vrabel to find the end zone.
Vrabel has caught TD passes in two straight Super Bowls and has five TDs in as many career catches, not bad for a linebacker - or anyone else.
Brady wasn't as fluid as he was when he won the MVP awards in the 2002 and 2004 games, but he was 23-for-33 for 236 yards and two TDs.
"It doesn't matter who gets what," Branch said of taking the MVP away from his quarterback.
Brady told CBS News Correspondent Jim Acostas: "I think everyone buys in to win. It's a selfless group of guys that's committed to try and do everything to win. And we do and we have a hell of a lot of fun doing it."
When the offense bogged down or turned over the ball, Harrison and his mates forced four turnovers, including a goal-line interception by the veteran safety. The Patriots also had four sacks, making Donovan McNabb look ordinary, even skittish at times.
And while Owens' return from a seven-week injury layoff was an individual success - he had nine catches for 122 yards - it was not nearly the star turn that Branch made.
Branch was most instrumental on the opening drive of the second half, which set the tone for New England's 57th victory in its last 74 games.
While New England handled frequent blitzes, Branch caught four passes for 71 yards on the series that ended with Vrabel's TD.
"We did a great job of adjusting during the game," Branch said. "It was physical; a lot of guys were bumped and bruised."
The Eagles responded with a 74-yard drive. McNabb whipped a 10-yard pass over the middle between two defenders to Brian Westbrook for the TD.
Still, as winners always do, the Patriots reasserted themselves, effectively using screen passes against a tiring defense. Even when Eagles defenders shouted to each other to watch for the screen, New England made it work, particularly on Kevin Faulk's 14-yarder that preceded Dillon's 2-yard run to make it 21-14.
Vinatieri hit his chip shot to make it 24-14. The Eagles came back on Greg Lewis' 30-yard TD reception with 1:48 remaining.
Not that it bothered the Patriots, not that anything seems to bother the Patriots. Here's a team that's losing offensive coordinator Charlie Weis to Notre Dame and defensive coordinator Romeo Crennel to become Cleveland's coach.
"When you're in the middle of it, you're not thinking about what you're doing," Weis said. "Dynasties are talked about 10 years later."
Sorry, Charlie, the Patriots are the talk of the league now.
Philadelphia's title drought goes on, but Owens certainly did his best to end it. The All-Pro receiver fulfilled his vow to start the Super Bowl, defying his doctor and playing with a metal plate and two screws in his right ankle.
"T.O. did a heck of a job," coach Andy Reid said. "I was proud of the effort and they battled, but we came up just short - too many turnovers - and against such a tough football team you can't do that."