Twenty years ago today, Star Trek: Deep Space Nine premiered. It was the second live-action spin-off of Star Trek, and the first that was set (and aired) at the same time as its immediate predecessor -- in other words, the Star Trek universe was, for the first time, expanding outward rather than forward, and focusing not on the voyages of starship called Enterprise but on the happenings at a space station.
Deep Space Nine was conceived from the beginning as a departure from The Next Generation; the color scheme of the uniforms, heavier on the black than those on the Enterprise, signaled a darker tone. It would be a major oversimplification to call DS9 a conservative show, but defining the ethos of the show against TNG -- which, especially in its first couple seasons, preached an almost childlike liberal utopianism -- sometimes gave it a conservative flavor, and that (along with strong characters, fine acting, sharp writing, and so forth) helped make it great.
Because it was set mostly on a space station jointly administered by Federation personnel but outside the Federation itself, DS9 could cheat on the preposterous Next Generation conceit of a future without money -- "currency could make a back-door re-entry into our story-telling," in the words of writer, supervising producer, and (in the later seasons) co-executive producer Ronald D. Moore, who would go on to develop the excellent Battlestar Gallactica reboot. The greedy Ferengi, conceived in TNG's first season as a villainous race that human characters compared to "Yankee traders" -- that's right, they tried to cast explicit analogues to American merchants as the villains -- were reinvented, and while they were often used as cartoon capitalists for comic relief, at times, particularly in Nog's stories, Ferengi ingenuity for positive-sum market transactions was portrayed as virtuous. (TNG, for its part, had by this time found a genuinely great villain in the hive-minded Borg, because, duh, collectivists make scarier enemies.)
More importantly, Deep Space Nine dealt with what Glenn Loury once called the essence of conservatism: The insight that human nature has no history. When the Federation sign a treaty with the brutal Cardassian Empire ceding planets inhabited by Federation colonists, the colonists dub themselves the Maquis, break away from the Federation, and start an insurrection against the Cardassians. Commander Sisko (later promoted to Captain) identifies the very progress that is so proudly touted by characters on TNG as blinding Federation policymakers to reality:
The trouble is Earth... On Earth, there is no poverty, no crime, no war. You look out the window of Starfleet Headquarters and you see paradise. Well, it's easy to be a saint in paradise, but the Maquis do not live in paradise. Out there in the Demilitarized Zone, all the problems haven't been solved yet. Out there, there are no saints — just people. Angry, scared, determined people who are going to do whatever it takes to survive, whether it meets with Federation approval or not!
I doubt that most of the writers of Deep Space Nine would identify as conservative (and Loury himself, though still idiosyncratic and interesting, has moved firmly to the left), but that can be read that as a critique of the Federation from the right, and it was quite a thing to hear on a Star Trek show.
Deep Space Nine dealt with terrorism in a nuanced way that would have been hard to pull off post-9/11. Kira, Sisko's second in command, committed terrorist acts she's "not proud of" as a Bajoran resistance fighter during the occupation, and struggles with adjusting to the new political order. The Maquis are left morally ambiguous. Anti-Federation Bajoran extremists are unambiguously malign. The Cardassian Liberation Front that allies with the Federation near the end of the series is unambiguously a force for good. All are called terrorists, and some even self-identify as such (though al Qaeda-style mass-casualty attacks on civilian targets we now associate with the word rarely figure in).
On the other hand, when the central conflict of the show became an existential struggle against a dangerous foe, DS9 dealt so unflinchingly with the necessary moral compromises made in war that it's hard to believe that some episodes were written in the pre-9/11 era. Federation officers don't order waterboardings, but they do commit (or tacitly cooperate with) acts that are arguably much worse -- and they don't stop being good guys.
Star Trek: Deep Space Nine is available in its entirety on Netflix Instant, which makes it easy to keep up with the serialized format (which undoubtedly hampered DS9's ratings in the pre-DVR era -- by the later seasons, it became extremely difficult to follow the story after missing an episode). If you're a fan of science fiction, it's worth revisiting, whatever your politics.