Final answer:
The custom that majority party members with the longest tenure become committee chairs in Congress is known as the seniority rule. This rule illustrates a form of traditional authority and gives senior members advantages in obtaining powerful positions within the congressional committee system.
Step-by-step explanation:
The custom followed in Congress specifying that majority party members with the longest record of service will become committee chairs is known as the seniority rule. This practice assigns committee chair positions based on a member's tenure and is indicative of traditional authority within the governmental structure. While committee chairs hold significant power over committee operations, it's important to note that there are limits; for instance, in the House, rules limit the tenure of committee chairs to prevent them from holding these powerful positions indefinitely. Rules also exist regarding senators' tenure in chair positions and their ability to serve concurrently as chairs or ranking members of other committees. Despite these restrictions, members with longer service have a distinct advantage when it comes to committee assignments and seniority rankings, which heavy-handedly influences who is chosen to lead.