“Another section says, ‘No State shall make or enforce
any law which shall abridge the privileges or immunities of
citizens of the United States.’ Another section says, ‘The
United States shall guaranty to every State in this Union
a republican form of government.’ The section last cited
contemplates a case where a controlling power shall strive
to have it otherwise, and the subordinated individuals need
protection. Congress is left the judge of what constitutes a
republican form of government, and consequently of the rights
incidental thereto.”