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.