It’s no surprise that the Duggar family is critically important to TLC. The long-running hit show “19 Kids and Counting” attracts millions of viewers every week — and by extension, millions of ad dollars — and has already spawned one spin-off.

And as the series debuted a new special on Tuesday night (“A Duggar Leaves Home,” in which Amy Duggar goes to Nashville to pursue her singing dreams), it’s very clear: The Duggars — parents Jim Bob and Michelle and their dozens of kids, grandkids, aunts, uncles and cousins — have quietly become one of the most powerful families on reality TV.

We mean this in the “under-the-radar” sense of the word “quiet. (With 19 kids and multiple grandchildren, the Duggars don’t really do anything without a lot of noise.)

While the unusual family gets its fair share of tabloid coverage, it’s not nearly as much as, for example, the Robertsons on “Duck Dynasty.” Plus, the antics of the Arkansas-based Duggar clan can’t begin to compete with, say, the Kardashians. The Duggars are deeply conservative, religious people who don’t kiss before marriage. The Kardashians … do other things.

Still, “19 Kids and Counting” has developed an extremely devoted fan base over the many years on the air: It started in 2008 on TLC as “17 Kids and Counting.” The series was in the Top 15 of cable shows across television last week, regularly tapping into key demographics.

Besides its millions of viewers, the power of the Duggar name cannot be underestimated, even in Washington. Last summer, conservative lobbying arm Family Research Council recruited the eldest Duggar child, Josh, to move to D.C. with his wife and three kids to become the executive director. As the Reliable Source noted at the time, “In hiring him, the group — known for its vigilantly anti-abortion, anti-gay marriage stances — hopes to appeal to more young people and to tap into the huge popularity of his evangelical clan within flyover America.”

In addition to writing multiple books about their lives, the family members are also popular figures to bring to GOP political rallies. They’re frequent guests on the “Today” show, among other programs.

And now, the potential spin-off: Though “A Duggar Leaves Home” billed as a special, in TLC tradition, it could easily turn into yet another series if things go well. It’s not quite the Kardashian-level number of shows on the same network (the first spin-off, “United Bates of America” about their family friends, didn’t last long) but it could trend in that direction.

The Duggar influence was addressed early on in the episode, in which the family’s quirky cousin Amy Duggar — the self-proclaimed “wildcard” who, unlike her cousins, wears pants instead of skirts and is allowed to date — heads Nashville to try to become a country music star.

“Just because my last name’s Duggar doesn’t mean a thing,” Amy, niece of Jim Bob and Michelle, explains as she packs to head to Music City. “I’m just a regular girl.”

That is, of course, is what people who get advantages always say. Sure, she’s got a long road ahead of her if she really wants to become a singer, but it certainly help that she has a camera crew and a potential reality show on her side. She stops by her cousin’s house for some encouragement and a cameo of the real stars of “19 Kids and Counting.” Uncle Jim Bob warns her that hundreds upon thousands of people come to Nashville every year to try to make it big — but she shrugs off the warnings.

Once there, Amy gets studio time with a producer, lands a private tour of the Grand Ole Opry, and has a spot at an open-mike night where there’s a record label executive in attendance. It goes okay — she freezes up at one point and has to start again. But the cameras corner the label exec at the very end, who admits while Amy looked nervous, she “looks forward” to possibly hearing more of her music.

If Amy’s musical journey continues, that just means that the Duggars have conquered yet another powerful realm of culture: the country music audience. With all these other endeavors, no matter how long their show lasts on TLC, it’s obvious that the Duggars aren’t going anywhere.