2012 NFL Power Rankings: Week 3 ESPN.com

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Another week, another new No. 1.

That's how tenuous the top spot has been so far in 2012. The Packers opened at No. 1, then dropped their season opener. The Patriots took over the top spot last week, then laid an egg at home against Arizona.

Now it's the 49ers' turn to experience life at the summit. Our voters (ESPN.com's John Clayton, ESPN.com's Ashley Fox, NFC East blogger Dan Graziano, AFC North blogger Jamison Hensley and NFC West blogger Mike Sando) made 2-0 San Francisco, impressive in all phases so far, a unanimous choice at No. 1.

Not that they weren't impressed by others. The Seahawks, thanks to a convincing victory over Dallas, made the biggest gain, jumping nine spots from No. 26 to No. 17. Arizona (up six spots) and Philadelphia (five) were also big movers.

There's potential for more significant moves in Week 3. The Broncos, smarting from a rough Monday night loss at Atlanta, host No. 2 Houston. Seattle can make even more headway by beating No. 4 Green Bay.

As for the 49ers, their grip on No. 1 appears firm (they play at No. 29 Minnesota). But as we've learned already in 2012, holding serve isn't easy.

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