Why might citizens choose to join political party

they could be part of a community of like-minded citizens

The Correct Answer is

They can be part of a community of like-minded citizens.

Explanation:

Citizens choose to join a political party for various reasons such as:

To change laws they see as outdated, or no longer representatives of the people's need. To address a specific need that they feel the current government is not responding. So they can learn about the American political process and how it works.