In Article I Section 2, the framers provided that seats the U.S. House of Representatives would be awarded to states “according to their respective numbers.” The “numbers” included immigrants, women, children, and other people ineligible to vote—lumped together as “free persons.” There were two exceptions to the rule: “Indians not taxed” (meaning those living under independent tribal governments) were not counted; and “other persons” (meaning slaves) were counted as three-fifths of “free persons.”
After Emancipation, there were no more “other persons.” Section Two of the Fourteenth Amendment, approved in 1868, now provides that apportionment is to be based on ”the whole number of persons in each State, excluding Indians not taxed.” Population, not voting rights, again. (In 1924, Congress granted citizenship to Native people under tribal government; there are no more “Indians not taxed.”)
Voting rights do appear in the Fourteenth Amendment, however. Immediately after the Civil War, Southern states were happy to have representation apportioned on the basis of the whole population of freed slaves, and not just at three-fifths of that sum, because it would have increased their number of House seats and electoral votes. They also planned to keep the franchise all white, thereby inflating the power of white, southern voters. The framers of the Fourteenth Amendment tried to forestall that, without using racial terms, by providing that when the right to vote “is denied to any of the male inhabitants of such State, being twenty–one years of age, and citizens of the United States, or in any way abridged, except for participation in rebellion, or other crime,” the states would lose representation for the entire excluded group. (That language has never really been tested; by 1870, the Fifteenth Amendment formally barred racial discrimination in voting altogether.)
Taken together, these provisions suggest that the basic constitutional rule of apportionment is, as the Reynolds v. Sims Court said, raw population. The three-fifths clause in 1787 and the “male inhabitants” clause in 1868 are phrased as extraordinary departures from that rule.
These provisions, of course, do not directly govern the issue in Evenwel. They apply to federal apportionment; the districts in this case are state legislative ones. The relevant constitutional provision, then is, the equal protection clause of the Fourteenth Amendment: “No state shall ... deny to any person within its jurisdiction the equal protection of the laws.” The privileges and immunities clause appears in the same section; it applies to “citizens of the United States”; equal protection, however, explicitly applies to every “person”—white and non-white, immigrant and native-born, citizen and non-citizen.
What right are we talking about? Is it the individual person’s right to representation? In a democratic system, leaders are elected by voters, but once elected, they represent all the people. Those too young to vote, those excluded because of criminal records, and those who are not citizens are “persons” for equal-protection purposes. Is it the individual voter’s right to an equal vote? Then voting-age population or something like it would be the correct basis for apportionment.