Likely unconstitutional. Per SCOTUS:
The right to vote is protected in more than the initial allocation of the franchise. Equal protection applies as well to the manner of its exercise. Having once granted the right to vote on equal terms, the State may not, by later arbitrary and disparate treatment, value one person’s vote over that of another. See, e.g., Harper v. Virginia Bd. of Elections, 383 U.S. 663, 665 (1966) (“[O]nce the franchise is granted to the electorate, lines may not be drawn which are inconsistent with the Equal Protection Clause of the Fourteenth Amendment”).