Question

What is at the top of the political party organization

Answer 1

It would be the national party

Answer 2

The national party is at the top of a political party's organization.

Volunteers are at the bottom of a political party’s organizational structure, but that does not mean they are unimportant.  Political parties' organization depends heavily on volunteers at the local and state level who will man office and phone lines, put out campaign signs, go door-to-door to each voters, etc.

Political political parties are organized at the local level (cities or counties), as well as at the state and national level.  Above the volunteers who serve on the front lines, there will also be local and state and national party leaders and committees.  The state and national conventions of each party play a key role in developing party platforms during each election cycle.  The national party leadership is at the head or top of all this organization.