Party leaders are blg fans of conventions because: Sponsors must swear that they know the candidate personally and consider him qualified for the office he is seeking.
The convention system gives them opportunity to take care of the other party business besides nominating candidates.
Candidates can judge whether they are in line with the rest of the party.
The party can fine-tune' its organization, finding where it is weak and working to correct the weakness,
They can rally the party faithful with platforms for debate and decisions,