Politics and fantasy might seem a peculiar combination. After all, one associates politics with real world conflicts, uncertainties, impending war, back-handed dealings, and lots and lots of unsavoury mud-slinging by politicians all around the world. Whatever does it have to do with the world of magic, elves, and spells? (Warning, may contain small spoilers)
If we look at the definition of politics, we see: "the activities associated with the governance of a country or area, especially the debate between parties having power"; "activities aimed at improving someone's status or increasing power within an organization." (Source: Google)
Once you put politics in the context of 'struggle for power', suddenly a myriad of published fantasy works spring to mind. A Song of Ice and Fire is rife with it, from the power struggles between families, the shifting border lines, the lucrative deals struck between families for alliance or for firepower, and the underhanded assassinations to secure ascension to higher powers. ASOIAF, for the history geeks, is obviously based on the Wars of the Roses: Lancasters (red rose) as Lannisters, York (white rose) as Starks, and possibly the Tyrells as Tudors. The dynamics in the Lancaster family reflects that of the Lannisters: an incompetent male leader, a scheming and string-pulling wife, a son on whom the wife dotes. The Yorks win several battles over the Lancasters, although Richard of York dies in battle and his son, Edward, then becomes king (Edward IV). Edward later marries a woman against his supporters' wishes and is killed when the Lancasters attack the Yorks, similar to the Red Wedding. Edward's two sons are captured and proclaimed illegitimate, reflecting on the claims on the two Lannister boys.
When Dumbledore publicly disobeyed the Ministry of Magic in Harry Potter, the ministry swooped in and revamped the school, brainwashing the students with essentially political propaganda. The students, in turn, formed Dumbledore's Army as resistance and struggled to regain control of their school. Snape's undercover mission was to uncover weaknesses in the enemy and utilise it for the greater good, becoming a pawn in the bigger power game.
Take it from another angle: dystopia is a sociopolitical issue multiplied tenfold. Dystopian fantasy thrives on politics. Society demands entertainment and is a fiercely unforgiving survival-of-the-fittest setting. Hype it more and make the participants teenagers and you have The Hunger Games, where Capitol controls whether people get to feed or starve, become rich or poor, become successful or snuffed overnight.