There’s never been a better time to fall in love with a cult TV hit — that show that fans and critics constantly rave about but always seems to be in imminent danger of cancelation.

These days, low ratings don’t necessarily mean a show’s days are numbered. There are so many ways to keep a series alive and to build its audience that if it demonstrates creative potential amid ratings bumps, chances are good it will stick around.

Of course, certain conditions apply.

High-end, serialized shows are faring especially well in this environment — skeins such as AMC’s Mad Men, Breaking Bad and The Killing or FX’s Justified and Sons of Anarchy. Never have TV networks and studios been as tolerant of low ratings for sophisticated serials, because what they may grow into is an unknown.

Moreover, if one network can’t tolerate a show’s ratings, another distributor might, as seen in the jumps of Friday Night Lights from NBC to DirecTV, Cougar Town from ABC to TBS and Southland from NBC to TNT, along with Netflix’s revival of Fox’s Arrested Development.

“Not so long ago, serialized shows were a difficult genre to program, and the underlying economic model didn’t really work,” says one distribution executive. “That paradigm has now shifted. … The networks have seen how well many serialized shows seem to be working, and Netflix has seen that binge viewing is a cornerstone of the experience that it offers consumers. Today, subscription video on demand (SVOD) complements whatever marketing a network is able to do for a show, and it makes up for the lack of a traditional syndication back-end, plus offers consumers the ability to catch up.

“It’s a virtuous cycle. It all works together to help the network boost ratings, and to make a show more popular and more ubiquitous.”

Serialized shows might launch with modest beginnings, but on-demand viewing and social media mean that the audience for these shows could explode at any moment. Some of today’s most buzzed-about, most critically acclaimed shows got there via steady growth.

Showtime’s Homeland climbed 35% in its second-season finale compared to season one. PBS’ Downton Abbey grew 65% compared with season two. And AMC’s The Walking Dead again set cable-ratings records with its third-season finale, outperforming all shows on television among adults 18-49 and pulling in as many as 15 million viewers overall.

All three of those TV powerhouses got that way, at least partly, because people couldn’t stop tweeting about them. Once word is out, curious viewers have the ability to catch up via cable on-demand, Netflix, the network’s website, iTunes or other methods. And once hooked, viewers are much more likely to show up when the show airs in pattern on the network.

Still, a show has a better chance of surviving if it airs on a cable network. Better still if it airs on a premium cable network.

“You have to distinguish between broadcast network patience and cable network patience,” says Kevin Beggs, prexy of Lionsgate Television Group, which produces Mad Men for AMC.

Mad Men has been a critical darling almost since its premiere, and Emmy named it top drama four years in a row before Homeland finally supplanted it last year. Mad Men never has garnered a big audience by television standards, but after the series was sold to Netflix in 2011 in a deal estimated to be worth between $70 million and $100 million, its season five premiere in 2012 jumped 41% to 3.5 million viewers, a series high. (Showing there can be a ceiling, for season six’s two-hour premiere April 7, viewership slipped just a bit to 3.4 million.)

FX prexy John Landgraf notes that while quality doesn’t guarantee survival, “it’s difficult to cancel” an acclaimed show.

“That critical acclaim accrues glory to your brand,” Landgraf says. “Even if it’s a small audience, it tends to be an important one on those elite shows.”

By contrast, Landgraf says when he was forced to cancel Terriers, a show that garnered tons of acclaim but few viewers, he couldn’t find any way to justify keeping it on the air. Like AMC’s Rubicon, also canceled after one season, Terriers didn’t become a watercooler kind of program.

“There was just a relentlessly downward trajectory of that show in the ratings,” he says. “No matter how I looked at it — in the live, live plus three, live plus seven, demos — it started weak, and the arrow pointed down all the way to the end. If at any point I felt like the people who clearly loved that show were successfully evangelizing it, I could have believed that it would have successfully built an audience over time, but I saw no information whatsoever that encouraged me.

“It’s difficult to stand up publicly and announce that something was a failure,” says Landgraf. “But you can’t make room for the next thing to bloom if you don’t acknowledge what’s happening and prune accordingly.”

One other factor: It helps a show if it’s cheap to begin with.

Comedies fall into this camp more than serialized dramas. FX’s Louie “puts up some pretty decent numbers when you look at its live-plus-seven ratings, but it’s not a numerical hit by FX standards,” says Landgraf. “It’s a solid mid-level player.”

“But when you consider who that audience is,” Landgraf adds, “in terms of people in the media and filmmakers and actors, it’s definitely people with whom we want to proselytize the FX brand. Louie is really, really inexpensive.

“The more money we invest in something, the quicker we’ll have to be on the trigger finger if it doesn’t work. The less money we spend, the more we can just let it rip.”

For all of the above reasons, broadcast networks are much quicker on the trigger finger — Do No Harm and Zero Hour, we barely knew ye — but broadcast series can benefit from great word-of-mouth and the ability to let viewers to catch up.

This season, Shonda Rhimes’ Scandal became a sleeper hit for ABC, tying CBS’ ratings monster NCIS as broadcast’s top-rated scripted drama among adults 18-49, and much of that was due to word-of-mouth. NBC’s Parenthood also attracts a small but loyal audience, and those who love it do so unabashedly. Lionsgate hopes that Nashville, which it produces for ABC, will benefit from that effect in season two.

“This is a show that we think is ideally suited to this new paradigm,” says Beggs. “It’s a high-quality, serialized drama, and it has potential to be a massive success. We’re already very pleased with the success and sales of the show’s music. It all points in the right direction.”

Finally, a low-rated show’s chance of remaining on the air is inversely related to how much success that network is having. It’s far more risky, for example, to fall head over heels with a series that’s winning only middling ratings on CBS, than with a show that’s performing similarly anywhere else. The big viewership for The Walking Dead  means that it might be hard for AMC to have the same amount of patience with its next Mad Men.

Says Landgraf: “It’s a fairly subtle art, deciding whether a first-season show that’s not lighting the world on fire eventually will.”