Wisconsin gerrymandering case: Here's what's at stake in Supreme Court ruling

Craig Gilbert | Milwaukee Journal Sentinel

Show Caption Hide Caption The Supreme Court Takes on Wisconsin's Gerrymandering Suit The Supreme Court Takes on Wisconsin's Gerrymandering Suit

The U.S. Supreme Court on Monday dismissed a challenge to the state's redistricting case involving Wisconsin’s GOP-friendly legislative map and sent it back to the district court.

The case was dismissed for lack of standing, but the court left open the broader issue of partisan districting.

At issue was whether it is unconstitutional to draw legislative districts in a way that significantly advantages one party.

When Republicans took power in Madison after the 2010 election, they enacted a redistricting plan that greatly enhanced their prospects of controlling both chambers of the Legislature, even in “down” cycles for the party, when it is losing statewide elections.

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The case, Gill v. Whitford, was argued last October. The Supreme Court took up the case after a three-judge federal panel struck down the GOP map in 2016.

What is at stake nationally?

Gerrymandering — drawing district lines to advantage one party — is a practice that both sides across the country have engaged in over the decades. But it has grown increasingly sophisticated thanks to an explosion in the availability of detailed demographic data and the development of more powerful mapping software.

But the same technology also makes gerrymanders more transparent. It is easier than in the past to measure and quantify the partisan “tilt” of a political map. In the short term, a decision that reins in gerrymandering would help Democrats more than Republicans. That’s because Republicans control more states, which has given them more opportunities than Democrats have had this decade to produce partisan maps.

What is at stake in Wisconsin?

If the Wisconsin map is struck down and the state is ordered to draw new lines, it could make the fight for the Legislature far more competitive than it is today. Control of the Assembly is not really in play under the current map. Too many seats favor the GOP.

Democrats do have of a chance of winning back the state Senate under the current map, but they are still at a disadvantage. It would take a large “blue wave” at the ballot box to shift control of that chamber based on the present lines.

How partisan is Wisconsin’s legislative map?

It is very partisan. In 2012, Democratic President Barack Obama won the statewide vote by almost 7 points, but Obama lost the presidential vote in 56 of 99 Assembly districts.

Based on the last three elections, more than 60% of the Assembly’s 99 seats are more Republican than the state as a whole. That means that in a 50/50 election year, when there are equal numbers of Democratic and Republican voters statewide, Republicans would be expected to win the Assembly by more than 20 seats.

Is the GOP’s advantage a product of gerrymandering or of the state’s population patterns?

The answer is both. Democrats have a natural disadvantage in district elections because they are more concentrated in urban areas such as Milwaukee and Madison, which confines the impact of the Democratic vote to a smaller number of seats.

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Republicans significantly enhanced that “natural” advantage by drawing the lines in a way that further expanded the number of GOP-friendly seats and reduced the number of Democratic-friendly seats. Another by-product of the map is less competition in individual Assembly races. The current map minimizes the number of competitive districts and maximizes the number of seats that are “locked in” for one party or the other.