The Anna Nicole Show, which looked to be the summer's breakout hit, has quietly been sliding down the ratings charts since its blockbuster debut.

In little more than a month, the show has lost more than half its audience. 

The Sunday-night reality show, detailing the often bizarre backstage life of zaftig model Anna Nicole Smith, premiered with a hefty 4.1 million viewers -- the biggest series premiere in E! history. 

But since then, it's lost viewers each week -- reaching a low of 1.8 million viewers on Sept. 8 before bouncing back slightly last Sunday night. 

The show that was supposed to be the successor to The Osbournes is slowly sinking in the west. 

"If you want to hold it against us that we had a phenomenal premiere, go ahead," says Mark Sonnenberg, E!'s executive vice president of entertainment. 

"The show is averaging close to a 2 rating. Yeah, compared to a 4 rating it's down . . . but it's still the highest-rated show on the network and has improved its timeslot average by almost 25 percent in households. 

"We could sit here and try to put a spin on it, but we got a phenomenal [premiere] tune in and a lot of people who checked that show out weren't our core audience," he said. 

Viewers and critics alike, some calling the show "train wreck TV," were initially fascinated by the behavior of Smith -- who seems at times punch-drunk and/or nearly inarticulate. 

So has that fascination worn off by now? 

"Anna Nicole is a curiousity and isn't as compelling as the characters on The Osbournes. This show is all about her, and after a while, it's a little tragic," says industry analyst Stacey Lynn Koerner of Initiative Media. 

"You either like her or you don't, you're either intrigued by her or you're not." 

Last Sunday's Anna Nicole Show did register an uptick in viewers -- gaining 300,000 eyeballs from the week before.

For more news, entertainment and sports coverage, click here for NYPost.com.