While Donald Trump's antics might be visceral and scary, they're nothing compared to the case being argued before the United States Supreme Court today.

Justices heard the case of Evenwel v. Abbott, which challenges the one-person, one-vote theory of redistricting which has been in effect for decades.

Jeremy Farris, writing for The Hill:

“One person, one vote” is a shorthand for a set of constitutional rulings handed down by the Court in the early 1960s. In a series of opinions, the Warren Court determined that each district electing a representative to a specific governmental body — from the U.S. House of Representatives to your local school board — should contain the same population. So, after each decennial Census reveals shifts in the population, state and local governments throughout the country redraw legislative districts based on the Census results to ensure that each contains the same number of people.

The plaintiffs in Evenwel v. Abbott, set for argument this week, are Texas voters who contend that this fifty-year-old, nationwide practice is unconstitutional. They point out that the Texas Senate districts in which they reside, although containing roughly the same number of people as other state senate districts, have more voters. Thus, the plaintiffs believe that their votes count for less and argue that the Equal Protection Clause of the Fourteenth Amendment requires Texas to redraw its senate districts to contain not the same number of inhabitants, but the same number of eligible voters.

If the Supreme Court agrees with the plaintiffs, it would redraw political power across the nation. A ruling in the plaintiff’s favor would apply to virtually every state legislative and local government body across the country. In so doing, the Court would shift political power and resources away from urban and suburban areas that have higher concentrations of persons ineligible to vote—e.g., children, undocumented persons, and felons. Consequently, cities across the country, including Los Angeles, Chicago, and Atlanta have opposed the plaintiff’s challenge.

SCOTUSblog has a report on the arguments:

This equality theory was neatly captured by Justice Samuel A. Alito, Jr. — although it was not clear whether he was really tempted to embrace it, or was just exploring its meaning. Suppose, he said, there was a rural district in which only nine percent of the population could vote, because its overall population is swelled by a large prison and none of the inmates can vote, but there is another district with about the same total population, but ninety percent of its residents can vote. “Is that okay?” he asked a federal government lawyer, Deputy Solicitor General Ian H. Gershengorn.

Gershengorn responded that the courts have recognized that legislatures, in drawing new districts, are entitled to rely on census data — that is, total population figures. There is no existing way, Gershengorn would go on to say, for the census to provide data that would aid legislatures in dividing up seats according to voter figures without simultaneously winding up with major differences in total populations. That, he indicated, would skew district population differences.

The theory was regularly disparaged by the more liberal Justices on the Court, who made clear they were not about to let the concept of representation be changed so that only voters were the constituents who counted in the writing of the laws. At least, they were not willing to make it unconstitutional to use total population as the starting point in redistricting, and mandating as the only constitutional norm the near-equality of voter populations among districts.

As usual, Justice Kennedy is considered to be the swing vote in this one.

Kennedy obviously was reacting to an argument that was stressed at the very outset on Tuesday, by Arlington, Va., lawyer William C. Consovoy that, in drawing up new election districts for Texas’s thirty-one state senate seats, the total population metric resulted in nearly a fifty-percent difference between the number of eligible voters in some districts compared to others. At most, Consovoy had later suggested, such a voter disparity should be closer to ten or twenty percent, at most.

Kennedy could see at least the surface appeal of that spread (as a Justice, he is constitutionally devoted to equality principles), and wanted to know why legislatures could not strive for equal districts and equal distributions of eligible voters. Why, he asked Keller, is Texas not required to accommodate both interests? Keller’s response was the same as Gershengorn’s: district map-makers, he said, have to rely on census data, “and all we have is total population.”

Kennedy next wondered if there were any studies about trying to achieve both. Keller said he knew of none, and Kennedy dropped this line of inquiry. A bit later, Keller added that, if the Court were to require a voter-based standard, that would wreak havoc with traditional districting principles, such as showing respect for local government boundaries.

Should the court toss decades of established practice in this case, it would be a disaster, for a number of reasons. First, because large swaths of the population who are still subject to the laws would have no voice in making those laws. They would be represented by someone who has no interest in representing their interests, whether they vote or not.

Second, because it would radically shift the power base from populated areas to rural, less populated areas, which would surely result in a Republican majority in all statehouses and the U.S. House of Representatives in perpetuity, given the more conservative bent of rural areas.

Stay tuned. This is going to be a huge decision, one way or the other.