The Super Bowl halftime show (search) — starring 62-year-old former Beatle Paul McCartney (search) — sent viewers scampering for a TV alternative, preliminary ratings showed Monday.

An estimated 86.1 million viewers watched the Super Bowl last Sunday, Fox said last night.

But that's the lowest viewership total in four years, since the 2001 Super Bowl when the Giants lost to the Baltimore Ravens.

Half-hour-by-half-hour ratings tend to show that viewership was rising just before the McCartney halftime show.

Last year's halftime show — staged by MTV and starring Janet Jackson — was marked by an infamous "wardrobe malfunction." This year, the NFL produced the halftime show itself.

Sunday night's audience dropped off steadily — despite being a tie game — after the beginning of the third quarter.

Still, Fox reported that — combined with the post-game show and a special episode of "The Simpsons" — it was Fox's highest-rated night of prime-time TV ever.

This year's Super Bowl audience was down about 4 percent compared to last year — when New England beat the Carolina Panthers.