What argument did La Follette use to show that primary elections are the foundation of government in a republic?

Robert La Follette established a primary election arguing that voters had the right to elect their candidates. La Follette represented the Progressive Movement of the United States and was governor of Wisconsin. He also wanted to have more competition within the political parties when choosing their candidates.

La Follette defended that in a republic citizens have the right to elect their representative by voting on them. Because of that, he said that citizens should be allowed to control all stages of the elections, including the primaries.