Final answer:
The primary process, which involves intraparty contests, is the cause of the highly fragmented character of political parties.
Step-by-step explanation:
The subject of this question is Social Studies.
The primary topic of this question is the selection process of political candidates in the United States.
The question is asking about the process that causes the highly fragmented character of political parties. The answer is the primary process, which involves intraparty contests. During primaries, candidates within a party compete against each other to secure their party's nomination for a specific elective office, such as a congressional seat or the presidency. This process can lead to the fragmentation of parties because it allows different factions within a party to nominate their preferred candidate, resulting in a diverse range of candidates representing the party.