Far more than a malfunctioning alarm clock, Meredith Vieira worried about disrupting The Streak when she joined NBC's "Today" show in 2006.

"Today" has won every week in the morning-show ratings since December 1995, according to the Nielsen Co. Last week the streak reached 15 years, or 783 weeks.

"My one goal was not to mess it up," said Vieira, who co-anchors the show's first two hours with Matt Lauer. "I didn't want to be the one in the anchor chair when we fell from first to second. I was really, really scared about that."

For good reason — she probably would have been blamed after replacing Katie Couric. Instead, the institution rolled on. This season, "Today" has averaged 5.3 million viewers, or 1 million more than its strongest rival, ABC's "Good Morning America."

Back in 1995, Couric and Bryant Gumbel were co-anchors at "Today." The show was two hours, half as long as it is now. The Rockefeller Plaza concert series had begun that summer. President Bill Clinton was in his first term. Lauer was in high school.

OK, that last part's not true — Lauer was the "Today" news anchor then. You get the idea: 783 to nothing is "a pretty incredible run," said the show's executive producer, Jim Bell. "It's unprecedented, I suppose."

The "Today" staff held a party last week for three occasions: to celebrate the streak, the holiday season and to bid farewell to NBC Universal chief Jeff Zucker, who will leave when Comcast takes control of the company. Zucker was the "Today" executive producer in 1995, and he rocketed up the corporate ladder in large part because of his success there.

"For so many people, they watch it because their parents watched it and their grandparents watched it," Vieira said. "There is a tradition to the show."

The winning streak is about more than pride. Zucker estimates the show has earned NBC $3 billion in pure profit during those 15 years. "Today" would have been profitable even without being No. 1, but not nearly to that level, he said

"In this era of highly fragmented television, with so many different options that viewers have, to be able to have that kind of a record every day is really quite extraordinary," said Tim Brooks, author of "The Complete Directory to Prime-Time Network and Cable Television."

"Today" pioneered the morning-show genre in 1952, and spent most of its history atop the ratings. The primary exception came in the late 1980s into the early 1990s, when the "Good Morning America" team of Charles Gibson and Joan Lunden was dominant.

Ending the current streak would take a powerful rival and a serious misstep by NBC, Brooks said. That's not impossible — "Today" seriously alienated its audience by replacing Jane Pauley with Deborah Norville two decades ago — but it hasn't happened lately.

Bell owes his job to the last time "Today" was seriously challenged. That was in the spring of 2005, when "Good Morning America" took advantage of a lethargic NBC and the sensation then surrounding ABC's "Desperate Housewives." During one week that May, "GMA" narrowed the gap to only 43,000 viewers, Nielsen said. NBC cleared the decks, firing Bell's predecessor even though he had never lost a week.

"The challenge definitely woke us up," Bell said. "It made us look at ourselves and how we were doing the show and change a few things. It reinvigorated us. We knew we had to fight for every viewer and for every booking."

That day-to-day competition is fierce, but one reason a serious challenge to NBC's reign may not be imminent is because the other two network morning shows essentially follow the same format. "The Early Show" on CBS is in the midst of changing its entire on-air team, but nothing has been said about changes to the content.

Several successful cable shows, like "Fox & Friends" on Fox News Channel and "Morning Joe" on MSNBC, follow the format of people sitting around and talking about the news. Even the Golf Channel is joining the party; it just announced the start of a two-hour morning show.

"It works," Brooks said. "The basic approach is one that people want in the morning."

Adding a third, then fourth, hour to "Today" carried the potential of diluting a powerful brand. Bell chose to walk the fine line of making those hours distinct but not so much that they didn't look like "Today." Ann Curry, Natalie Morales and Al Roker host the show's third hour, with the bawdy team of Kathie Lee Gifford and Hoda Kotb taking over for the fourth.

Bell praised his staff for hard work and camaraderie, pointing out as an example the elaborate video the "Today" on- and off-screen team (with a Brian Williams cameo) made to a Black Eyed Peas song recently for a weeklong feature where the `Today' cast remade popular viral Internet videos.

A naturally viral video from a week ago may be more illustrative. Lauer is interviewing finance correspondent Jean Chatzky for a finance segment and he gets the giggles when there's a reference to the a size of "the package."

Vieira is egging him on from beyond the camera's range.

"I couldn't imagine doing this job if you didn't get along with the people you worked with," she said.

___

NBC is owned by General Electric Co.