Acaucus is an election, which determines the number of electoral votes for each candidate. a meeting of party members to select delegates to their national convention. the meeting wherein a state announces its electoral votes. the meeting, which determines who the party's vice presidential candidate, will be.

a meeting of party members to select delegates to their national convention.

Explanation:

A caucus in the US states is a formal meeting or conference where the local members of the political party or the legislative body  nominates their preferred candidates among candidates those who are running for office after many speeches and debates . At Caucus party delegates are also selected to attend their national convention.

Therefore the answer is --

a meeting of party members to select delegates to their national convention.