Why TV’s ‘Smash’ went splat What happened?

Katharine McPhee portrays Karen Cartwright in the NBC series “Smash.”

“Smash” is decisively not living up to its title.

It didn’t start out that way. The NBC series (10 p.m. Mondays), which revolves around the making of a Broadway musical about Marilyn Monroe, premiered in February to 11.5 million viewers, a godsend for a network whose prime-time lineup is holding on by a thread, or, more specifically, a mindless singing competition (“The Voice”).

NBC quickly renewed “Smash” for a second season and executives almost certainly began plotting “Law & Order: Broadway.”

Then fans started abandoning ship. The show now draws about 6 million a week. Cast members must be dreaming about being booked for something more respectable — like the Spider-Man musical.

It can only get worse. Creator Theresa Rebeck won’t be returning next season, and a changing of the guard this early in a show’s run is never good news. Just ask fans of ABC’s “Commander in Chief,” who threw the Geena Davis series out of office after Rod Lurie was replaced by Steven Bochco.

And then there’s the question of what happens when the show’s fictional musical, “Bombshell,” premieres, an event that occurs during the May 14 finale. I can just imagine a very special episode next season about the fallout after a performance is interrupted by a ringing cellphone.

So what went wrong so quickly — and how can networks avoid making this mistake again? A review of nearly all 15 episodes and a look back at other fast-fading series suggest the following:

Don’t oversell yourself. “Smash” had so many ads leading up to its premiere, you’d think Katharine McPhee was running for president. Sure, that helped the premiere, especially because the campaign was tied to NBC’s airing of the Super Bowl the previous night. But with heavy promotion comes weighty expectations, ones that few shows can uphold.

Fox made such a big deal about having Steven Spielberg, who is also attached to “Smash,” as a producer on “Terra Nova” that audiences expected “Jurassic Park IV.” Instead, they got a gritty update of “The Swiss Family Robinson.” Needless to say, “Terra Nova” is now extinct.

Audiences don’t need Oscar-winning advisers and relentless publicity. Just ask the

folks from “Seinfeld,” “CSI” and “Cheers,” shows that actually benefited from soft launches.

Face the music. I’m a big fan of the original songs Marc Shaiman and Scott Wittman have penned for the show. The ballad “Secondhand White Baby Grand” should be recorded by a pop diva, like, yesterday. But viewers seem to prefer familiar tunes, judging by the success of “Glee.”

Don’t make us haters. The biggest debate among “Smash’s” dwindling fans isn’t about which character is their favorite, it’s about which is most annoying. The leader of the pack appears to be Ellis “I just heard something” Boyd (Jaime Cepero), a two-faced assistant who’s such a weasel he makes Eddie Haskell look like Captain America.

My personal vote goes to the musical’s producer, Eileen Boyd, if only because she’s played by Anjelica Huston. That’s actually kind of a compliment. An Oscar winner and the daughter of a film legend shouldn’t be downing shots in dive bars, playing “Big Buck Hunter” and shacking up with a scruffy bartender.

Movie stars don’t make compelling characters on the small screen. HBO’s “Luck” was officially canceled because several horses died, but it didn’t help that it was one of the channel’s least-watched shows. Dustin Hoffman and Nick Nolte are fantastic actors, but we were hesitant to invite them every week into our living rooms, especially if the good china wasn’t out.

Don’t try so hard. The theater world may be fraught with massive egos and backstage betrayals, but “Smash” takes it way too far. A kid running away from home because his parents might be separating? Check. Switching Marilyns as often as most people change their toilet paper? Check. Watching your lead actor abandon the show two days

before the curtain rises? Check.

You can admire a series with so much ambition, but that doesn’t mean you have to love it. Nonetheless, “Smash” will probably have a second chance next season, a rare luxury these days, but only because it’s on a fourth-place network.