Packing and Cracking Districts

Partisan gerrymandering refers to the practice of drawing electoral district maps with the intention of favoring one political party over another.” Both Democrats and Republicans engage in partisan gerrymandering when in control of redistricting.

With partisan gerrymandering, minority party members can’t elect candidates in proportion to their statewide support for that party. Techniques mainly involve packing and cracking. When you pack minority party members into a smaller number of very safe districts, you waste minority party votes. Cracking minority party members apart dilutes or eliminates their ability to elect a candidate in either district. In addition, pairing minority party incumbents in one district or drawing them into unwinnable districts undermines incumbency advantage.

How do you know if partisan advantage predominated in drawing a district? Mathematicians and political scientists have been busy. They identify two general approaches. The first,  partisan symmetry, looks at the relationship between district outcomes and statewide vote shares. Map-simulation methods model thousands of maps using local criteria and geography to identify whether the plan is an outlier. Clear partisan gerrymanders reveal as extreme outliers. 

In deciding that federal courts would not entertain Constitutional challenges to partisan gerrymanders, the Supreme Court majority tied their understanding of the measures before them as calling for proportional representation. The Supreme Court has long required district by district analyses and rejected proportionality.

If minority party voters and racial and ethnic minorities correlate highly, partisan and racial gerrymandering look nearly identical. This could apply especially in South Carolina where we register to vote by race but not by party.

The next post will address ongoing efforts to curb partisan gerrymandering after Rucho v. Common Cause

John C. Ruoff, Ph.D.

The Ruoff Group

Dr. John Ruoff has been involved in redistricting since the mid-1980s. He has drawn and evaluated maps for every level of single-member districts in South Carolina, from boards of public works to the U.S. Congress, including the last three rounds of statewide redistricting. He has testified and consulted as an expert in redistricting and Voting Rights court cases.

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