Voices & Choices

Competition under Arizona’s Independent Redistricting Commission

Competition under Arizona’s Independent Redistricting Commission

One common complaint with the United States’ electoral system is that congressional elections are woefully uncompetitive. Later tonight, we’ll receive Arizona’s U.S. House results. Most of those results will not come as a surprise. Seven of Arizona’s nine congressional districts are completely safe for the party that holds them. A popular scapegoat for this problem is gerrymandering, or the deliberate drawing of district lines to benefit the party in charge of the state legislature.  Many point to independent redistricting commissions as the reform that will restore competition in Congress. Arizona adopted an independent redistricting commission in 2010.

To test whether an independent redistricting commission is an effective means to create competitive elections, we examined competitiveness in Arizona’s congressional districts between 1984 and 2012 (the full results will be soon released in our The Impact of Redistricting Reform in the Southwest report). Arizona’s districts were drawn by three different institutions in three different decades:

  • In 1982, the state legislature drew the boundaries.
  • In 1992, after negotiations in the state legislature came to an impasse, the U.S. District Court adopted a plan submitted by a member of one of the state’s Indian tribes.  The “Indian Compromise Plan” was more compact, better represented minority and Native American communities and avoided the deliberate drawing of district lines to protect incumbents.
  • In 2000, Arizonans voted to enact a constitutional amendment that created a five-member independent redistricting commission, which drew the state’s congressional and state legislative districts in the 2002 and 2012 redistricting cycles.

Three very different line drawers. So, were elections under the court-adopted map and the independent redistricting commission map entirely more competitive than the old partisan drawn map?

Not really.

One way to measure the impact of redistricting reform is to look at the number of safe districts in the state. A safe seat is one in which the district’s Democratic partisanship is more than 8 points from 50 (ie. is less than 42% Democratic or more than 58% Democratic). Though the number of safe districts in Arizona decreased after the introduction of the 1992 court-adopted map, the trend reversed in 2004 in a map drawn by the independent commission. In 2012, three-fifths of the state’s districts were safe (Figure 1).  Right before the 2016 elections, seven out of Arizona’s nine districts were safe, and the state contained zero swing districts. 


Another way to look at competition is to consider how many races were won by small margins. The number of House races with a margin of victory (MOV) smaller than 10% has fluctuated dramatically in Arizona (Figure 2). Under the map drawn by state legislatures in 1982, there were no margins of victory less than 10%. Right after the court-drawn map was introduced, the number of races with an MOV smaller than 10% increased, peaking at one-third in the 1998 midterms. After the 2000 independent redistricting commission was established, the number of races with MOVs less than 10% decreased, but remained higher than in the 1980s.

These trends are similar to the national trends, in which the percentage of seats with a margin of victory less than 10% increased in the 1990s as the Republicans took back the U.S. House, but returned to pre-1990 levels in the 2000s. The notable exception is that Arizona was worse than average in the 1980s, indicating that taking power out of the hands of the state legislature has some impact. 


Taking power out of the state legislatures is clearly a step forward. But neither of the two measures studied here point to a game changing or consistent increase in district competition under court-adopted or independent commission drawn maps.  The vast majority of Arizonians still vote in uncompetitive elections that are won by large margins, where there is little doubt months ahead as to who is going to win.

The political geography of the United States might be helpful in explaining the lack of impact of Arizona’s adoption of a court-drawn map or its establishment of an independent redistricting commission.  Bill Bishop argues in his book The Big Sort that Americans “self-gerrymander” by preferring to live with politically like-minded neighbors; Democrats tend to cluster in cities whereas Republicans can easily be found in rural areas. With this political geography, it is very difficult to draw competitive districts.

Independent redistricting commissions are an important reform. They restore voter confidence in the electoral process and ameliorate the cynicism that depresses turnout. However, we might also consider additional reforms such as the top-four primary or fair representation voting  to give voters more choice and improve competition in congressional elections. 

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