The subject of lawsuits challenging gerrymandered legislative districts has been relatively quiet since the Supreme Court's decision in Vieth v. Jubelirer back in 2004.  In that case the Supremes essentially found the whole subject of whether a redistricting has been used by one political party to disadvantage the other to be non-justiciable in almost all cases.  (Racially-based gerrymanders remained an exception.)  Prior to that decision, the courts had from time to time entertained challenges to particularly egregious gerrymanders, but had struggled to come up with any coherent generally-applicable test to distinguish the permissible from the impermissible.  In such ambiguous circumstances, almost any redistricting could bring forth a barrage of lawsuits.  Really, in the absence of any clear standard for what you could and couldn't do, it would almost be political malpractice for the winners of the most recent elections to fail to redistrict in a way to disadvantage their opponents at least a little.  

Vieth put an end to most of the endless litigation; but it did not quite completely end the issue.  That's because Vieth was what is called a plurality opinion.  Four judges joined the main opinion (written by Justice Scalia); four dissented (in three separate opinions written by Justices Stevens, Souter and Breyer); and the final justice, Kennedy, joined with Scalia on the result, but with different logic.  Basically, Kennedy agreed with Scalia that nearly all political gerrymanders are non-justiciable, but held open the door just a teensy crack that if one was bad enough it could be challenged:

A decision ordering the correction of all election district lines drawn for partisan reasons would commit federal and state courts to unprecedented intervention in the American political process. The Court is correct to refrain from directing this substantial intrusion into the Nation’s political life. While agreeing with the plurality that the complaint the appellants filed in the District Court must be dismissed, and while understanding that great caution is necessary when approaching this subject, I would not foreclose all possibility of judicial relief if some limited and precise rationale were found to correct an established violation of the Constitution in some redistricting cases. 

And what, pray tell, is the "limited and precise rationale" that might justify federal judicial intervention into a redistricting process conducted by a state legislature?  Kennedy forthrightly admits that he is unable to articulate it -- it's just that he doesn't want to foreclose forever even the possibility that somebody some day might come up with such a thing.  Meanwhile, each of Stevens, Souter and Breyer took a crack at the challenge, coming up with three different proposed tests.  And Scalia ridiculed the whole project, pointing out that not only were three different tests proposed in this case alone, but prior case law contained multiple proposed tests which were also different from the ones proposed by the dissenters.

Fast forward twelve more years.  Justice Scalia has died.  Justices Stevens and Souter have left the court.  And a three-judge District Court panel in Wisconsin, by a 2-1 vote, has just invalidated the 2011 redistricting plan adopted in Wisconsin by its legislature, in a case called Whitford v. Gill. It seems that when the 2011 redistricting came along, Wisconsin's Republicans had just retaken control of the state legislature and undertook to redistrict to their advantage.  In the 2012 election, for example, the plaintiffs in the case claimed that the Republicans won 48.6% of the votes for the state Assembly, but 61 of 99 seats.  Shocking!

There's no way this decision would pass muster under Scalia's plurality opinion in Vieth, so these judges must be playing to Justice Kennedy.  What, then, is the "limited and precise rationale" adopted by this court that would support judicial intervention only in egregious cases?  Here is the test that this court articulates:

[T]he First Amendment and the Equal Protection clause prohibit a redistricting scheme which (1) is intended to place a severe impediment on the effectiveness of the votes of individual citizens on the basis of their political affiliation, (2) has that effect, and (3) cannot be justified on other, legitimate legislative grounds. 

Doesn't sound very "limited and precise" to me, but what do I know?  (By the way, in case you are interested, the majority opinion was written by Judge Kenneth Ripple, who normally sits on the Seventh Circuit and was appointed by President Reagan.  The judge who joined the majority is Barbara Crabb, appointed by President Carter; and the dissenting judge is William Griesbach, appointed by President George W. Bush.)  Dissenting judge Griesbach makes a number of good points in his opinion, including that a far more egregious gerrymander in Indiana was upheld by the Supreme Court in 1986, and that a concept called the "efficiency gap," cooked up by experts for the plaintiffs, makes no sense as part of some kind of constitutional standard for gerrymandering cases.  The "efficiency gap" purports to be a measure of the effectiveness of each voter's vote toward actually electing a representative, and is calculated by comparing the number of votes for candidates of each party to the number of legislative seats won by that party.  The plaintiffs had offered the "efficiency gap" as their effort to find the "limited and precise" rationale that Justice Kennedy is looking for; but the majority did not use that "gap" as the deciding factor, and rather relied on it only as evidence of supposedly wrongful partisan intent.

In latching onto the "efficiency gap" concept, even if not as the sole gravamen of its decision, the court's majority essentially bought into a fallacy.  Sorry guys, but even in the absence of gerrymandering, there is no inherent reason why the percent of seats in a legislature should match, or even be be very close to, the percent of voters who vote for each party.  For example, consider a state with an electorate that is about 55% Democrat and 45% Republican, with the voters of each party evenly spread throughout the state; and assume that there is a complete absence of gerrymandering.  It is entirely possible that the Democrats would win every single seat, and highly likely that they would win way more than 55% of the seats.  As another example, the Conservative Party (Tories) in England often win an absolute majority of seats in Parliament even though they win only around 40% of the vote.  This happens because their opponents split the left-wing vote among multiple parties.  

Anyway, this Wisconsin case now goes direct to the Supreme Court under an unusual procedural statute that sends this type of case to three-judge panels first and then straight to the Supremes. For reasons stated, I think the reasoning of the case is weak, and maybe even so weak as to fail to attract some or all of the "liberal" votes on the Court.

If the subject of gerrymandering intrigues you, I'll give you a couple of additional situations to ponder.  In the world of naturally-occurring factors causing a big "efficiency gap" for voters in the absence of (very much) partisan gerrymandering, consider my own home state of New York.  In both national and local elections, our state-wide electorate in recent years has voted consistently about 55-60% Democrat and about 40-45% Republican.  Theoretically, a perfect gerrymander orchestrated by Democrats could give them nearly every seat of both houses of the legislature and of the Congressional delegation.  To achieve that result, the redistricters would somehow have to assign collections of Democratic New York City voters to upstate districts, creating a map that no one can even imagine.  In the real world, New York has what might be viewed as a "natural gerrymander" that substantially favors the minority Republicans.  The Democratic voters are concentrated in small areas (mostly New York City, plus upstate cities like Buffalo and Albany), while the Republicans are spread across the state in large areas where they have small but consistent majorities.  In any map of reasonably contiguous and compact districts, the Republicans continue to win large numbers of seats.  Result:  the Republicans just won 9 of 27 Congressional seats, and they actually have control of the State Senate!

And then there is the United States as a whole.  For the second time in just the last five elections, the Republicans have won the electoral college in a presidential race while losing the popular vote.  If the state boundaries had been drawn by an evil cabal of back room Republicans, it is hard to imagine that they could have come up with a much better gerrymander of the United States for electoral college purposes than the state boundaries as they exist.  The Democratic votes are heavily concentrated in a few places (California, New York, Massachusetts, Illinois, Maryland, D.C.), where they are then "wasted" (in the terminology of the Whitford case).  Here are a couple of extreme scenarios that are completely possible given our state boundaries as drawn:

1. In the recent election, Hillary Clinton won the popular vote in California by about 3.5 million votes, and in New York by about 1.5 million votes, for a margin of about 5 million votes from just those two states.  Consider a future Democratic candidate who wins just those two states by the same margins, while the Republican wins all the other states (and even D.C.!) by margins of 100,000 per state.  The Democrat wins the popular vote by 100,000, while the Republican wins the electoral vote by 454-84.
2. Or consider an election in which the Democrat wins all the states won by Clinton, and by the same margins as Clinton, while the Republican wins the states won by Trump, but by only 100,000 per state.  The electoral college majority for the Republican would be the same as Trump's 306-232 margin over Clinton, but the Democrat would have won the popular vote by some 10 million or so, while losing the election.

This all seems to be working to the tremendous advantage of the Republicans these days, but remember that it was not always so -- and the pendulum could easily swing back.  Probably the most famous gerrymander in my lifetime occurred when the Democrats took control of the legislature of formerly-Republican California in time for the 1981 redistricting.  California's house delegation promptly went from a 21-21 Democrat-Republican split to 28-17.  That handiwork was not overturned in court, but so offended the voters that they ultimately imposed a redistricting commission system.  Meanwhile, California has become so heavily Democratic that its Congressional delegation has gone to 39-14, even in the absence of (egregious) gerrymandering.