This chapter explores two major frameworks for understanding political parties: the UCLA Theory of Parties and the candidate-centered model. The UCLA Theory posits that parties are dominated by interest groups and activists who shape platforms to advance narrow goals rather than broad voter preferences. The candidate-centered model views parties as coalitions of ambitious politicians seeking to maximize votes and win elections by taking positions distinct to each candidate. History offers evidence for both models. Candidate-centered parties tend to be more accountable to the public because candidates will be more responsive to the median voter than special interests that play a strong role in party primaries.