A recurring idea in many Science Fiction works is that, during space conquest, planets will form a kind of feudalistic system, each governed by a sort of monarch or noble. I believe that won’t be the case despite some interesting premises that say otherwise.
Large distances will mean independence from the home planet and also a different path of evolution. Also, new planets, won’t have a large population from the beginning. This means a lot of fragmentation and isolation and feudalism thrives in such conditions. Also, terraforming or simply building infrastructure at a planetary level requires large resources and a lot of political will, presumably easy to achieve if both are in the same place.
But I believe such systems will not form. I don’t think people will give up democraty so easily, politics and elections will continue. We see that local politics get more attention (more people vote at the local level then at the state level). Resources will come from economics, a more efficient way to gatter them. Political will, at the local level, will be more focused and variation will ensure that no excesses appear.