Ingroup or Outgroup Leader Influence? (Barber and Pope 2018 Robustness Section Reanalysis)


In their article “Does Party Trump Ideology? Disentangling Party and Ideology in America” recently published in the journal American Political Science Review, Michael Barber and Jeremy Pope present a very compelling, important, and timely study. Investigating the extent of party loyalty and the “follow-the-leader” dynamic among the American public, the authors test how partisans react to flexible policy position-taking by President Donald Trump—and one similar case study for Barack Obama—with a survey experiment. The main finding is striking: on average, when Trump takes a conservative position on a policy issue Republicans express more conservative beliefs on that policy themselves, and when Trump takes a liberal stance Republicans too become significantly more liberal as a result. The latter exemplifies blind leader adherence best—even when Trump takes positions outside of his party’s mainstream ideology, mass members of his party still become more likely to adopt his stance.

What about Democrats?

A common reaction to this finding has been questions about partisan (a)symmetries. The study concerned Republican members of the public and their current leader in Trump most. Should we expect the same dynamic among Democrats in blindly following a comparable leader in their party? To address this, Barber and Pope discuss a robustness analysis towards the end of their paper (in the subsection “Robustness: Other Political Leaders as Tests”) that tests for leader effects among Democrats using Barack Obama as the cue-giver. Specifically, they exploit the close similarity between a new immigration asylum policy from Trump—introduced in the spring of 2018—and the policy stance by the Obama administration a presidency earlier (both policies said families/children, when arrested by the border patrol, will be held in a detention facility before an asylum hearing). The leader cues in support of the policy can thus be credibly interchanged (i.e. experimentally manipulated). In an experiment, partisans were randomly told either 1) that this is Trump’s policy, 2) that this was Obama’s policy, or 3) no cue, after which they expressed how strongly they agreed (a value of 5 on a 1-5 scale) or disagreed (1) with the policy.

Barber and Pope describe their results and the implications of them in the following way:

“The results show large effects for Democrats and smaller, but still statistically significant effects for Republicans…

…Democrats are also willing to adjust their preferences when told that the policy was coming from Obama…”

Separating out Ingroup and Outgroup Cues

Though not explicitly stated, the purpose of this robustness study is to test whether evidence of strong in-group partisan loyalty and influence from leaders within the same party appear for Democrats as well. Because partisans are exposed to both Obama and Trump cues, results from this experimental design can speak not only to ingroup dynamics, but outgroup dynamics as well. The analysis approach used in the article, however, cannot distinguish between these two forces possibly at play. This is because outcomes from the experimental control condition (no exposure to a leader cue) are omitted from the analysis. Specifically, to calculate the effects (appearing in Figure 6 in the actual article), the treatment variable makes use of just the Trump cue and Obama cue conditions. The displayed treatment effects are just the difference in policy opinion between these two conditions.

Original analysis

Below is a graph reproducing the results in the original article (with replication data) using the original analysis approach: regressing the policy opinion variable on a binary variable that—for Republicans—takes on a value of 1 if the cue comes from Trump and a value of 0 if it comes from Obama (and the opposite for Democrats). Thick bars represent 90% confidence intervals and thin ones are for 95% confidence intervals. (Note: The original article shows 0.22 instead of 0.23. This is due to differences in rounding up/down.)


Democrats agreed with the policy by 1.18 points less when told it was Trump’s compared to being told it was Obama’s. Republicans agreed with the policy by 0.23 points more when it came from Trump (vs. coming from Obama). It is not clear, though, whether these effects are driven more by partisans following ingroup leaders on policy (Democrats following Obama), or being repelled by outgroup leaders (Democrats moving away from Trump’s stance). Fortunately, this can be separated out. Instead of comparing average opinion levels between Trump and Obama cue conditions, it would be more informative to compare the average in the Trump cue condition to that in the control condition, and the average in the Obama cue condition to that in the control (and again, split by respondent partisanship).


The below plot presents results from setting the control condition as the reference group in distinct “Trump cue” and “Obama cue” treatment variables, which predict policy opinion among Democrats (left-hand side) and Republicans (right). The Obama cue estimate and confidence interval appear in purple while those for the Trump cue appear in orange.

barberpope2_022019After breaking up the cue effects like this, the result for Republicans is no longer significant at conventional levels. The Obama cue treatment does not move their opinion much, while the Trump cue moves them 0.18 points more supportive, but the effect is not significant.

Of course, the key part of this study is opinion movement among Democrats. In making use of the control condition, this reanalysis reveals that the outgroup leader effect from Trump is nearly twice as large as the ingroup leader effect from Obama on mass Democratic opinion, though both dynamics are at play. When told the immigration asylum policy was Obama’s policy during his presidency, Democrats become 0.42 points more supportive relative to the control. This effect is statistically significant, and provides evidence of what this robustness study was seeking: mass Democrats following their own leader on policy. When told the policy is Trump’s, Democrats react more strongly, becoming 0.76 points more opposed to the policy compared to the control (also statistically significant). To sum up, the ingroup follow-the-leader effect certainly arises for Democrats in this study. But the reported treatment effect was driven in larger part by a reaction to an outgroup leader’s expressed stance—a dynamic different than the one at the heart of the original article.


Beyond clarifying this part of Barber and Pope’s paper, the specific result should not come as that much of a surprise in the context of related literature. In his 2012 article “Polarizing Cues” in the American Journal of Political Science, Stephen Nicholson uses a survey experiment to find that when party leaders take a position on housing and immigration policies, mass partisans from the out-party move significantly away from this leader’s position. (For example, Republicans oppose an immigration bill substantially more when they hear Obama supports it versus when they don’t hear his position.) Thus, this particularly strong reaction to an outgroup leader cue in Barber and Pope’s robustness study—which likely incited negative partisanship—makes sense.

[As an interesting aside, Nicholson curiously does not find strong evidence for ingroup leader persuasion; partisans don’t follow-the-leader much. This contrasts with Barber and Pope’s main results: as Figure 1 in their paper indicates, Republicans follow their ingroup leader in Trump a considerable amount, but Democrats do not react that negatively to an outgroup leader (Trump) in expressing their policy opinion. Future research should address this uncertainty, paying special attention to 1) cue type (actual leader names? anonymous partisan Congress members? party labels?), 2) study timing (during a campaign? right after one when a president’s policy orientation is not as clear?), and 3) policy areas (will attached source cues be viewed credibly by respondents? do the issues vary by salience level?).]

Do Only Republicans Follow-the-Leader? No

Where does this leave us? To reiterate, the purpose of this robustness study was to check whether the follow-the-leader dynamic was not specific to Republicans (as the main study results may imply) but rather common to all partisans. The experiment does indeed support the idea that Democrats also sometimes follow-the-leader on policy opinion—just not as much as the original results may have indicated.

Moreover, other pieces of evidence support a view of partisan symmetry for this behavior. In the first part of a working paper of mine that builds on Barber and Pope’s article, I evaluate how partisans form their opinion in response to policy positions taken by leaders outside the party mainstream (a liberal position by Trump for Republicans, a conservative one by Obama for Democrats). In both cases, partisans follow their respective leaders. For example, when told Obama has expressed support of a major free trade bill that was previously proposed by Republican legislators, Democrats move 1.11 points more supportive of the bill (on a 1-7 scale) compared to no exposure to an Obama cue.

Second, panel survey evidence by Gabe Lenz in his 2012 book “Follow the Leader? How Voters Respond to Politicians’ Policies and Performance” is also telling. One of the case studies Lenz uses is George W. Bush’s policy proposal to invest Social Security funds in the stock market during the 2000 election (his opponent, Al Gore, opposed it), and how this became the most prominent policy debate during the campaign. From August to late October of 2000—during which the issue became particularly salient—Lenz finds that Gore supporters change their policy opinion most to bring it in line with their leader’s (Gore’s stance of opposition). Given that Gore supporters are more likely to be Democrats, this serves as another example of Democrats following their leader on policy. These pieces of evidence—along with Barber and Pope’s robustness study—thus show the follow-the-leader dynamic cuts across partisan lines.

Ingroup or Outgroup Leader Influence? (Barber and Pope 2018 Robustness Section Reanalysis)

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