The Court's decision in Baker v. Carr was properly cast in terms of protecting individual rights under the equal protection clause, for this issue can be distinguished and separately handled. It does seem inevitable, however, that the decisions which set standards by which to determine invidious discrimination will also by these standards delineate, at least in broad outline, one aspect of what will be considered an acceptable "republican" form of government guaranteed by the Constitution.
William M. Hames,
Baker v. Carr -- Malapportionment in State Governments Becomes A Federal Constitutional Issue,
15 Vanderbilt Law Review
Available at: https://scholarship.law.vanderbilt.edu/vlr/vol15/iss3/23