This exclusive new preview clip for Battlestar Galactica season 4 reminds us why the science fiction series' violent moral ambiguity has made it the most compelling political drama on TV. Sure the show is about humans fleeing for their lives from cyborgs in space, but it has a realistic, ripped-from-the-headlines urgency that 24 could only dream of. Even the basic BSG premise sounds familiar: Separatists with a burning desire for religious purity have launched a coordinated nuclear attack on our heroes, who are themselves struggling in a mire of corrupt political leadership and a military gone mad with power. It just so happens that the separatists are cyborgs called Cylon and the heroes are from a star system halfway across the galaxy from us.

What pleases about BSG, for a mainstream audience not necessarily inclined to freak out over spaceships, is the careful way the show's creators David Eick and Ronald Moore have created an entire political system for the characters to inhabit. We aren't just motoring from battle to battle. Instead, we watch as the human president fights with political pretenders and the military for power over the few thousand people left after the Cylon attack. There are press conferences and elections, worker strikes and Cylon sympathizers. The humans even become suicide bombers at one point.

This isn't a show that gives us a simple, Star Wars-style good vs. evil fairy tale. Everyone, even the steely Cylon, are ambivalent and ethically fungible. With next season concluding the epic tale of the human and Cylon battle to reach Earth and colonize it first, the action is sure to be intense. But don't expect the meaty political allegory to fall by the wayside. Things are just starting to get interesting.

We'll be watching characters dealing with a legal battle over who is to blame for last season's witchhunts, where accused Cylon collaborators were summarily executed without trial. And the Cylons have started having children with humans, raising the question of whether the us vs. them, human vs. machine binary really makes sense at all.

It's possible that what allows BSG to be so overtly political, complete with subplots about suicide bombing, is precisely the fact that it's set in a science fictional world. There is a narrative comfort zone for audiences: We don't have to worry that what we're watching is about ourselves because it takes place in a fantasy world. And yet there's no mistaking the fact that the characters in BSG are us. And I don't just mean the humans. We are the Cylon too.

The new season of BSG starts airing Friday, April 4 on the Sci Fi Channel.