The Secret Service began protecting some presidential candidates in 1968. The first minor party or independent presidential candidates who ever received such protection were John G. Schmitz, 1972 nominee of the American/American Independent Parties, and Dr. Benjamin Spock, 1972 nominee of the Peoples Party. Eugene McCarthy received such protection in 1976. John Anderson received it in 1980.
Ross Perot did not want such protection in 1992 nor in 1996. He had his own security and did not want the federal government to constantly know where he was.
Thanks to Eric Garris, Darcy Richardson, Theresa Amato, and Clay Mulford for help with this post.