"in the early 1800s, the system of nominating presidential candidates that left the candidates beholden to their parties' leaders in congress was called "

king caucus

The term “caucus” originated in the United States, to mean a meeting of supporters of a particular party. This system referred to as “king caucus” was used to nominate presidential candidates during 1800. After 1824, two candidates from the Democratic-Republican Party condemned this system and replaced it with national presidential nominating conventions.

map scale refers to the relationship (or ratio) between distance on a map and the corresponding distance on the ground. for example, on a 1: 100000 scale map, 1cm on the map equals 1km on the ground.