What Happened in the Arizona Senate Election? (2018)

Please note: The analysis below is based on an initial estimate of the 2018 electorate. Catalist released an updated analysis of the 2018 electorate in May 2019.


January 18, 2019

Author: Zachery Crowell, Analyst

  • First, Sinema banked a significant number of votes in the last two weeks of early/ absentee voting.
  • Second, among voters of color and Latinx voters in particular, turnout rates and support levels in 2018 were closer to presidential election levels than prior midterms like 2014.
  • Third, Sinema substantially increased the Democratic margin with urban and suburban voters while moderately increasing support among white rural voters.
  • Finally, she managed to persuade a significant share of 2016 third-party voters who voted in 2018.

The margin shifts between midterms and presidential years, in large part, can be attributed to the people of color voting population being older and slightly less Democratic leaning than during presidential elections. When looking at those who voted in Arizona in both 2018 and 2016, it is clear that those modeled to be voters of color without a college degree shifted very little in their preferences. Sinema won these voters by a margin of 44 percentage points and Clinton won the same voters by a margin of 45 percentage points, for a shift of 1–2 points. Thus the majority of decline is attributed to older non-white non-college voters being both more likely to vote and vote Republican in midterm elections than their younger peers. (Note: Age breaks used in the development of the two-way support estimates shown in the graph above may produce more stark looking discontinuities between age groups.)


In addition to voting increasingly Democratic, the suburbs were a larger share of the vote in 2018 than any time since 2008, due to a combination of population growth and differential turnout:


Furthermore, we can find clear geographic patterns at the Census tract-level. (Note: As some areas of Arizona are quite rural and sparsely populated, some of the Census tracts mapped above may have very few residents. This is an important consideration when comparing patterns over time.)

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Thank to Michael Frias.