Final answer:
The process where party members gather to discuss and select election candidates and form a political platform is termed a caucus. It marks the beginning of the nomination process and involves various informal voting methods.
Step-by-step explanation:
In the context of the American political system, the process by which active party members meet in small groups to decide the candidates to represent the political party in an upcoming election and to help shape the party's political platform is known as a caucus.
A caucus is characterized by members of a political party gathering at a set time and place to debate and choose the candidate they believe best represents their party's values and goals. This process signifies the beginning of the formal selection of a political party's nominee for local, state, or national elections.
Caucuses are less formal and less expensive than primaries and involve methods of voting that are quite diverse, like dropping marbles into a jar or taking a voice vote. They also provide a platform for party members to select delegates who will represent their choice at the party's state or national-level nominating conventions.