NBC has renewed its glitzy musical series “Smash” for a second season — taking a chance the show can catch on better next year.

The Monday-night series, which centers on the behind-the-scenes drama at a Broadway musical based on the life of Marilyn Monroe has averaged a little less than 8 million viewers a night thus far.

Those are middling numbers at best. But “Smash” is doing well in the advertiser-coveted “young” demo of adults age 18-49 (it’s the network’s top-rated show in that category).

“Smash,” which premiered to a huge promotional campaign in early February, stars Katharine McPhee, Anjelica Huston and Megan Hilty and cast Post theater columnist Michael Reidel as himself in several episodes.