Negatively it aided him thereto, by laying the penalty of a decreased representation upon any State that should deny or in any way abridge his right to vote at any election for the choice of electors for President and Vice-President of the United States, representatives in Congress, the executive and judicial officers of a State, or the members of the Legislature thereof.
-- The Fifteenth Amendment, now proposed, did not attempt to declare affirmatively that the negro should be endowed with the elective franchise, but it did what was tantamount, in forbidding to the United States or to any State the power to deny or abridge the right to vote on account of race, color, or previous condition of servitude.

States that should adopt an educational test or a property qualification might still exclude a vast majority of negroes from the polls, but they would at the same time exclude all white men who could not comply with the tests that excluded the negro.

In short, suffrage by the Fifteenth Amendment was made impartial, but not necessarily universal, to male citizens above the age of twenty-one years.
The adoption of the Fifteenth Amendment seriously modified the effect and potency of the second section of the Fourteenth Amendment.

Under that section a State could exclude the negro from the right of suffrage, if willing to accept the penalty of the proportional loss of representation in Congress, which the exclusion of the colored population from the basis of apportionment would entail.

But the Fifteenth Amendment took away absolutely from the State the power to exclude the negro from suffrage, and therefore the second section to the Fourteenth Amendment can refer only to those other disqualifications never likely to be applied, by which a state might lessen her voting population by basing the right of suffrage on the ownership of real estate, or on the possession of a fixed income, or upon a certain degree of education, or upon nativity, or religious creed.