Final answer:
The system of nominating presidential candidates in the early 1800s that involved party leaders in Congress selecting the nominee, which Andrew Jackson criticized as 'King Caucus,' was eventually replaced by national party conventions and the presidential primary election system.
Step-by-step explanation:
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. This process involved party leadership meeting without input from grassroots members to pick their preferred candidate. The term "King Caucus" became associated with this method following the criticisms by presidential candidate Andrew Jackson. Over time, to weaken the national party leadership's grip, state party leaders and grassroots reformers pushed for a national party convention. Eventually, the rise of the presidential primary election season sought to end the influence of King Caucus and allow for a more democratic nomination process.