The convention is a meeting held by a politcal party following its precint convention for the purpose of electing delegates to its stae convention.

County convention

Explanation:

 The county convention is one of the type of political convention in the united state that held after every 4 years following by its specific precinct convention.

In the county convention, only the registered candidates and also particular selected delegates can participate in the county convention.  

The main purpose of the county convention is that the delegates and all the alternates are elected for its stae convention in the legislative district.

 Therefore , County convention is the correct answer.