It doesn't necessarily need to be about politics, but I think the setting is interesting.
The only one I can think of at the moment is Pan's Labyrinth.
For later dramatizations of the dictatorship: La mala educación (Bad Education) directed by Pedro Almodóvar/Cuéntame cómo pasó (TV series)/Amantes (Lovers) directed by Vicente Aranda
Most films made about the Franco dictatorship after the transition to democracy (1975-1981) tend to emphasize the social, sexual, and cultural stagnation of Francoist life. Sex is usually a prominent theme in these films, since the post-transition viewed the Franco dictatorship as sexually repressive.
For some good films from the Franco period: Bienvenido Mr. Marshall (Welcome, Mr. Marshall) directed by Luis García Berlanga /Rojo y negro (Black and Red) by Carlos Arévalo
The above films might be hard to find, and I don't know if there are subtitled versions. Rojo y negro is on YouTube but it's in Spanish.