Question

another name used to describe third parties is _____.
independent parties
communist parties
mainstream parties

Explanation:

In political systems, third parties are those that operate outside the two dominant mainstream political groups. They are often referred to as independent parties because they are not affiliated with the major, established parties. Communist parties are a specific ideological type of party, not a general term for third parties, and mainstream parties are the opposite of third parties.

Answer:

independent parties