[rayiner]

If people are bound by a constitution, created by the best minds of the day, which specify a government of limited powers not amenable to democratic expansion, then what is that but rule by philosopher kings?

Note that the U.S. Constitutional scheme is not one of minarchist government. The powers of the federal government are limited to those enumerated, but the scheme presupposes the existence of state governments, whose powers are nearly unlimited.[1] Moreover, the Constitution guarantees that these state governments will have republican form.

[1] More or less, the states were considered to have inherited the sovereign powers of the British Parliament, which were limited only by unwritten British constitution (i.e. the historical rights of Englishmen).