Which term represents a way to pick delegates that is used in 15 states, in which rank-and-file party members attend a neighborhood meeting, share ideas and concerns about candidates, and cast a ballot for pledged delegates to attend a statewide meeting?

Nomination caucus

Explanation:

Hi! The answer to your question would be nomination caucus. Nomination caucus is the name for informal meetings in which American congressmen would agree on whom to nominate for the Presidency and Vice Presidency from their political party. In this case, this would be the delegates that meet to share ideas and concerns about candidates.