When the off-network run of NBC skein “Smash” launches tonight, the Ovation network will be doing something NBC couldn’t: Banking on Broadway.

Differences of scale between Big Four net NBC and smaller basic cabler Ovation make the gambit viable — and make Broadway fans the focus of attention for Ovation in a way they never could be for NBC.

Second-season viewership for “Smash,” which opened at 4.5 million and slipped to 2.4 million for the finale, qualified it as a flop for NBC. By comparison Ovation, according to Nielsen, averaged 70,000 people tuned in during primetime to the arts-focused net during the first week of May.

“By Ovation standards, ‘Smash’ would have been a hit at any point during its NBC run,” said Robert Weiss, Ovation’s chief creative officer. “For us not to tap into those passionate fans would be a huge missed opportunity.”

Many members of the Broadway industry loved to hate “Smash,” and media coverage linked the skein, which wowed critics in its first episodes before shedding their support over the course of its run, with the phenomenon of “hate-watching.” But well beyond those Gotham-based legit insiders is a demo of theater enthusiasts who are among the more than 200,000 weekly theatergoers averaged by Broadway, and are also counted in the 750,000 followers of the “Smash” Facebook page.

To hold on to those legit fans, Ovation will follow episodes of “Smash” with a half-hour panel, “Broadway Bash,” that will use the preceding “Smash” segs as the basis for a broader theater discussion. Based on the lineup for the first episode — thesps Daisy Eagan, Gabriel Burrafato and Allen Hidalgo with choreographer Spencer Liff, who appears in the “Smash” pilot — the L.A.-filmed series doesn’t seem likely to sate Main Stem insiders hoping for a writers-room breakdown of how and why the TV series turned out the way it did.

But Ovation, in 50 millions homes via cable, satellite and telco, is aiming for a broader crowd around the country. Scoring even a relatively low percentage of those “Smash” fans would rep a big win for Ovation, currently looking to boost its profile with 200 hours of original programming that will also include new nonfiction series “The Art Of:,” “Music Mavericks” and “Culture Pop.” In addition, Weiss envisions extending “Broadway Bash” in order to hang on to those theater types even after “Smash” ends its off-network run.

For NBC, the Rialto fans who tuned in to “Smash” ended up being a drop in a big, mostly empty bucket. But for Ovation, that same demo has become something it’s almost never been to film and TV: Statistically significant.