Michael Barone‘s latest column for the Washington Examiner focuses on the U.S. Supreme Court’s apparently endless consideration of standards states must use when drawing election maps.

Fifty-one years ago the Supreme Court handed down its one-person-one-vote decision, requiring that within each state congressional and legislative districts must have equal populations.

That gave redistricters a relatively easy standard to meet. Census data provides block-by-block population counts every 10 years, and it’s possible now to draw lines for districts so that their populations are identical or vary by just one person.

But redistricting cases keep making their way to the court nonetheless.

One reason is that the Voting Rights Act amendments of the 1980s have been interpreted as requiring the creation of a maximum number of districts with majorities or near-majorities of black or Hispanic residents. This has produced many grotesquely shaped constituencies and much litigation.

This month the court heard two other redistricting cases. One, Evenwell v. Abbott, was brought in Texas. The plaintiffs argue that districts should be equal not in total population but in number of eligible voters. They live in areas where almost all adult residents are citizens, but in other areas — the Lower Rio Grande Valley particularly — a majority of residents aren’t eligible to vote, because they are non-citizens or children.

As a result some districts have two to three times as many eligible voters as others. That’s not equal representation, plaintiffs argue. …

… The other redistricting case heard last month, Harris v. Arizona Independent Redistricting Commission, raises the issue of whether a plan in which district populations vary by 10 percent can be invalidated because it favors one party. Here the court has an opportunity to set a standard that will cut back on its redistricting caseload.