Reviewing Data on the Individual Level Stability of Partisanship Entering the Trump Era

Recently, there’s been renewed interest in the question of how stable partisan identification is, especially with respect to what it means for Donald Trump’s approval rating numbers. Some have questioned the common belief of partisanship’s fixed nature, motivated by potential change introduced by the Trump presidency. This prompts the question of what evidence exists that can shed light on whether the Trump era has ushered in substantial party identification change at the individual level. I’ll quickly summarize relevant data here, focusing on available panel datasets that include a wave before (or at least in the early parts of) the Trump era and another wave sometime during the Trump era (around the 2016 election or after).

1. Voter Study Group, wave 1 in December 2011 and wave 2 in July 2017: VSG 2011-2017: 86 percent of 2011 Democrats and 87 percent of 2011 Republicans maintain the same partisan affiliation six years later, while the D->R conversion rate is 6 percent (among 2011 Democrats) and the R->D rate is 3 percent (among 2011 Republicans)
2. Pew Research Center, wave 1 in December 2015 and wave 2 in March 2017: 88 percent of 2015 Democrats and 87 percent of 2015 Republicans stay constant in their partisanship two years later; the D->R shift is 10% and R->D is 11%, though greater some turnover occurs in the intervening time period
3. GfK Ltd., wave 1 in October 2012 and wave 2 in October 2016 (from Mutz 2018 who made data public): 94 percent of 2012 Democrats and 96 percent of 2012 Republicans maintain the same partisanship four years later; D->R rate is 5 percent and R->D is 3 percent (one note: the public dataset didn’t include weights, so these are unweighted percentages)
4. CBS/YouGov: waves in January 2017 and July 2017 show 92 percent of Democrats and 90 percent of Republicans stay constant in party identification, while the D->R rate is two percent and the R->D rate is three percent; strong partisanship stability and low switching rates also appear in comparing waves from February/March 2017 and May/June 2018
5. YouGov 2015-November 2017 (from Bartels 2018): although partisan consistency rates are not reported, party switching is again very low as only four percent of 2015 Democrats become Republican in 2017 and five percent of 2015 Republicans become Democrats in 2017

In sum, across several sources of survey data and survey modes (though three out of the five are YouGov-based), the evidence points to individual level partisanship being very stable and altered very little in the era of Trump presidency. Moreover, the direction of the little partisanship change that has occurred is inconsistent across survey source (in some cases the D->R shift is larger, in others it’s the opposite). A next step might be to historically contextualize these rates of partisan stability and change around the time of presidency transitions with previous ones, and thus get a better sense of what this recent change means. Compared to the period before Trump entered the political scene, for example, the rates of partisan constancy and change as of late look even less exceptional. Namely, in the 2010-2014 CCES panel dataset, 92 percent of Democrats and 90 percent of Republicans stuck with the same partisan affiliations over the course of four years (D->R was two percent and R->D was three percent).

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