The Star Wars villain is disenchanted with the ruling, conservative Popular Party and rips up his party membership card in the ad for Podemos, which after a strong start in early 2015 is currently trailing in fourth place in the polls.
The video is titled "the change awakens" a play on the title of the new Star Wars film, The Force Awakens.
In the two minute long video, Darth Vader receives a letter, signed by Jedi master Yoda and with a purple postage stamp of Podemos leader, the pony-tailed Pablo Iglesias.
Then after a period of deep pondering he appears to jettison the forces of darkness to consider a brighter future.
The advert is a publicity campaign for Podemos’ "postmen and women of change" initiative, launched in early November, in which the party calls on supports to spread the "message of change" that Spain needs a different government after the December 20th general election.
Podemos members and supporters are being encouraged to write personal letters that call for a "change in the whole of Spain" and distribute them around their local neighbourhoods.
The advert is a clever tie in with the recent publicity surrounding the latest film in the Star Wars saga, which is released on December 18th in Spain.
Excitement is brewing around the country; superfans recently took part in the ninth annual Star Wars parade in Barcelona.