I think chapter 10 is an important chapter to review for the specific incidents that detailed political change. Three major events occured that address political change.
1. It is determined that a facility is to be made to educate the young pigs and new behaviors among the pigs arise. For example, others are expected to get out of the way when a pig approaches and pigs are allowed to wear ribbons on certain days. The education of some but not all directly sets a precedence for who will be ruling in future generations.
2. The humans come to meet with the pigs and they share drink, game, and conversation. This marks a friendship that was before forbidden.
3. The pigs begin walking on two feet and acting like humans. This demonstrates the political change of becoming exactly what the animals had hoped to get away from.
A good place to start for this is the list of commandments that the animals have drafted as the foundation of "Animalism." As the novel progresses, the commandments are broken, thereby signaling political changes in the animals' community. For example, one of the commandments calls all humans enemies; however, Napoleon eventually takes counsel with the farmers for business. By this time, Napoleon has been developing his role as a dictator, and his dealing with the humans signals a shift away from the heart of "Animalism."