This term was common in Mexico during the reign of the PRI, when the president and leaders of the party would handpick the next person to run for president (and the candidate won without fail for over 70 years).

Mi sugerencia.

an insider action is something done secretly within a organization: for instance, two bosses agree privately that Mr. X is going to be promoted, although there are other employees more deserving of promotion. In the end very few people know the real reason why Mr. X was promoted.

dedazo

Nepotism (favouring family members, literally your nephew for posts, in its original sense, Roman origin) means that the person who is going to get a post/a project etc has been chosen not on merit but on connections, and although the post/project may be advertised and the motions have to be gone through, the chosen one will be successful.