After 16 years and 852 weeks, the Today show's reign as America's highest-rated morning show is over. According to Nielsen, Good Morning America averaged 5.147 million viewers last week to Today's 5.134 million. If the numbers hold up, it would mean an end to one of the most impressive streaks in TV history. Is Good Morning America now officially the number one morning show? Here, a brief guide:   

They're only 13,000 viewers apart. Is that really a big deal?
Symbolically, at least, it's huge, says Jon Friedman at MarketWatch. The last time Today failed to top the weekly ratings, Bill Clinton was in the first term of his presidency and Mel Gibson was the toast of Hollywood for Braveheart. Plus, says Scott Collins at the Los Angeles Times, in addition to the 13,000 extra pairs of eyeballs watching GMA, the ABC show is trending in the right direction. Its ratings are up 7 percent from the same week last year, while Today's are down 9 percent.

How did GMA pull off this win?
Largely through star power, says Chris Ariens at Mediabistro. On Wednesday, The View co-host Sherri Shepherd spoke on GMA about being kicked off the hugely popular Dancing With the Stars, and on Friday, New York Jets quarterback Tim Tebow appeared with his mom. Those appearances both helped propel GMA to victory over Today.

Are there any asterisks?
You bet. GMA's ratings win came during a week when popular Today host Matt Lauer was on vacation. And among viewers aged 25-54, the most desirable demographic to advertisers, Today still bested GMA, which means that advertisers aren't going to start abandoning NBC, says Brian Steinberg at Ad Age

What is NBC saying?
For its part, Today is being gracious. Producer Jim Bell beamed that the show's 852-week streak is "one of the most incredible achievements in television history," before conceding that "we tip our caps to the team at Good Morning America."

Will GMA stay on top?
Maybe not, says Collins. Even this victory might be shortlived. Nielsen's figures are only preliminary, and when the final tally comes out on Thursday, GMA's margin of victory could very well be erased. Even ABC acknowledges that possibility, saying only that the network is "cautiously optimistic" that the victory will stand. Regardless, says Friedman, the continued ratings war between the two networks "will be fun to watch, no matter how it turns out."

Sources: Ad Age, Entertainment Weekly, Los Angeles Times, MarketWatch, Mediabistro, New York Times