They were first mentioned by the political philosopher John Locke. He was very influential for the founding fathers who based the ideas of rights that are self evident on his philosophy. According to him, the natural rights were those of life, liberty, and property, a bit different than what ended in the final documents.
The answer for your question is the 3rd answer
I would say his popularity came from his pledge to restore 'order' in the country which was plagued by mass unemployment and strikes by socialists and communists. His blackshirts beat up socialists and communists. Obviously the socialists and communists opposed his rise as did many other working class people. Some of the middle class shopkeepers, doctors, lawyers etc worried about the rise of socialism in the new Soviet Union also supported him.
