Why Are State Conventions and Platforms of Little Importance to What

Why are state conventions and platforms of little importance to what nominees say and do?

A) Candidates for public office are nominated in primaries rather than in conventions.
B) Candidates raise their own campaign funds independently of the party.
C) Candidates need to gather support from the large number of voters, not the small number of party activists.
D) Party organizations in the United States are generally quite weak.
E) ​centralized