Which principle of government was at the center of the conflict during the Nullification crisis?

The principle of government that was at the center of the conflict during the Nullification Crisis was the principle of states' rights versus federal authority.

Here are the steps to understand this:

1. The Nullification Crisis occurred in the early 19th century when the South Carolina legislature declared that the federal Tariffs of 1828 and 1832 were unconstitutional and therefore null and void within the sovereign boundaries of the state.

2. The tariffs favored northern manufacturing interests over southern agricultural concerns, and South Carolina, under the leadership of John C. Calhoun, argued that states had the right to nullify federal laws that they deemed unconstitutional.

3. This brought up the principle of states' rights, which is the idea that the union binding the United States is an agreement between the states and that they therefore can reject federal laws they regard as infringing on their rights.

4. On the other side was the principle of federal authority, upheld by President Andrew Jackson, which is the idea that the federal government has the power to make and enforce laws that are binding upon all states.

5. The crisis was resolved when a compromise tariff was passed in 1833, but the underlying conflict between states' rights and federal authority continued to be a major cause of dispute in American politics, eventually contributing to the outbreak of the Civil War.