David Gans at Slate:

In Texas and a number of other states, voters age 65 and older have the right to vote by mail for any reason, while younger voters generally have to cast ballots in person. As a result, it is harder than it should be for millions of voters to cast a ballot, solely because of their age. Cascino v. Nelson, the case challenging Texas’ second-class treatment of younger voters, is one of the most important voting rights cases before the courts, yet it has flown under the radar. Next month, the Supreme Court will consider whether to add it to its docket.

In Cascino, the plaintiffs urge the Supreme Court to strike down Texas’ discriminatory law as a violation of the 26^th Amendment’s guarantee that the “right of citizens of the United States, who are eighteen years of age or older, to vote shall not be denied or abridged by the United States or by any State on account of age.” SCOTUS has never interpreted the meaning of the amendment, which was ratified more than half a century ago….

The Framers of the 26^th Amendment consciously wrote it to parallel the Constitution’s separate prohibitions on racial and gender discrimination in voting contained in the 15^th and 19^th amendments, respectively. Transcending partisan divisions, Democrats and Republicans agreed that discrimination against younger voters had no place in our democracy. As Rep. Richard Poff, a Republican congressman from Virginia, insisted: “Just as the 15^th amendment prohibits racial discrimination in voting and just as the 19^th amendment prohibits sex discrimination in voting, the proposed amendment would prohibit age discrimination in voting.” In short, these three amendments prohibit all voting discrimination on account of the protected characteristic—race, sex, or age—without exception.

If a state sought to confer the right to vote by mail solely on white persons or men, it would be quickly struck down as a stark violation of the 15^th and 19^th amendments. Under the 26^th Amendment, age discrimination in voting is equally suspect. The amendment forbids laws that classify voters on account of age and deny equal voting opportunities to younger voters. Texas’ two-tiered voting system is precisely what the 26^th Amendment forbids.

What does Texas say in defense of its discriminatory regime? Its main justification is that the right to vote does not include the right to vote by mail. But nothing in the text of the 26^th Amendment—like that of the 15^th Amendment and other voting rights amendments—carves out voting by mail from its coverage and permits blatantly discriminatory voting laws. Having chosen to allow voting by mail, Texas cannot discriminate against voters on the basis of age and deny them the right to cast mail-in ballots. Younger voters, no less than voters 65 and older, are entitled to exercise their fundamental right to vote without having to endure countless hours of waiting at a crowded polling place.