Which factor contributed to the decline of political machines?

The passage of civil service reforms.

Explanation:

A political machine is a political group that relies heavily on a small group or a single leader, and the support of businesses that they can gather. Most of the time, these followers receive a reward for their effort. Political machines rely heavily on patronage and long-standing political ties. These were very common in the United States. However, with the passage of civil service reforms in the late 19th and early 20th centuries, this became more difficult, as public servants needed to be better qualified, with credentials becoming more important than connections.

answer; andrew jackson approved nullification by signing it into law,and john calhoun opposed it saying it was unconstitutional;

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