Answer:
Popular Sovereignty
Explanation:
The Progressive Era was a period of social activism and political reform in which many civilians participated (direct democracy) in order to reform the vertical (hierarchy) political system. Among the targets were the political machines with their corrupt and malfunctioning representatives.
Popular Sovereignty, that dates back to the Enlightenment, is the purest of (and most horizontal) democratic government, in the sense that the goverment´s purpose should be to protect (the civil rights) and serve the people, and not the other way around. And if they fail to do, or are corrupt or both, so they should be replaced.
It brought the USA into a war that up till now they were trying to stay out of. It also caused the creation and use of the first nuclear bomb
because they could not just take slaves away they just stoped them from bring it back but they finaly took it away in in 1807 with the 13 amenment
