Briefly: The authors argue that mobilization has the strongest effects on voters who are indifferent about turning out. Efficient campaign managers should identify these fence-sitters and mobilize only them; money spent mobilizing those who are likely to turn out (or stay home) regardless of the campaign’s efforts is money wasted. Crucially, however, the authors demonstrate that these indifferent voters are not the same from one election to the next. In highly visible elections (like presidential elections), mobilization efforts should target those who rarely vote; in obscure elections (like legislative primaries), mobilization efforts should target those who regularly vote; and in mid-level elections (like Congressional or mayoral races), mobilization efforts should target those who vote occasionally.

Contribution to the Literature

This argument resolves a conflict in the literature between four different models of mobilization, which the authors summarize in their figure 1 (at right; click to enlarge). In panel A, mobilization influences all voters equally; in panel B, mobilization influences those who would be least likely to turn out otherwise (that is, mobilization has the strongest effect on “low propensity” voters); in panel C, mobilization has the strongest effect on high-propensity voters; and in panel D, mobilization has the strongest effect on voters with a moderate propensity to vote.

Although the authors reject panel A, their theory can produce a theory that can lead to either B, C, or D. In high-salience elections, panel B is accurate–since in high-salience elections, it is low-propensity voters who are debating whether to turn out. In low-salience elections, panel C is accurate–since it is the regular voters who are debating whether to turn out.

Empirical Test

For empirical evidence, the authors re-evaluate the results of 11 previous experiments.² They use turnout among each study’s control group as a proxy for salience. They estimate each voter’s “propensity to vote” using a bunch of demographic variables (mostly) and past turnout data. Sure enough, they confirm their theory.

Critique

The authors characterize a voter’s propensity to vote as an “enduring, individual-level trait.” I find this puzzling. It is well-known, for example, that turnout rises with age (to a point). We also know that voting can be habit-forming; a voter mobilized in one election becomes more likely to turn out in subsequent elections (Green and Shachar 2000; Gerber, Green, and Shachar 2003; Fowler 2006). Of course, I doubt that this measurement choice undermines their results.

On the whole, though, a welcome contribution. Campaign consultants should read this closely. When political scientists spend NSF money on mobilization experiments, they can use a blanket strategy. But when campaigns spend hard-earned dollars on mobilization efforts, they need to know exactly which voters to target.

Update: Research published by Catalist, a Democratic group, seems to support this paper’s conclusions. Read more here.

Or maybe–just maybe–voting is “contagious.”¹

The trouble is, it is difficult to prove empirically whether voting is contagious. To do so requires somehow controlling for selection effects and other outside factors. In the article reviewed here, Nickerson reports on an innovative experiment that does just that. Ahead of the September 10th, 2002, Congressional primaries in Denver and Minneapolis, Nickerson sent canvassers door to door to households that had (exactly) two registered voters. At each household, the canvasser gave a brief message to whomever answered the door. Based on random assignment, each household received either a “get out the vote” (GOTV) appeal or a placebo message about the importance of recycling.²

There are actually two experiments going on here. The first tests the direct effect of delivering a GOTV appeal to whomever answered the door. Consistent with previous experiments, Nickerson finds that this group voted at a rate 9.8 percentage points higher than the placebo group.

The second experiment is far more interesting. For it, Nickerson looks at turnout rates among those who did not answer the door. Those who did not answer the door at houses receiving the GOTV message voted at a rate 6.0 percentage points higher than those who did not answer the door in the placebo group. This is the contagion effect.

In other words, 61.2% of the treatment effect was passed on from the mobilized voters to their housemates.³ This is huge. Nickerson points out that this “contagion effect” has a stronger effect on turnout than education, income, or age.

Of course, every study has its shortcomings. Experiments like this are the gold standard for making a causal claim. However, experiments also suffer from external validity problems–that is, this study’s conclusions may not apply in every circumstance. Nickerson points out several potential concerns. Among them:

• This study looks only at two-voter households. But what about college roommates, multi-generational households, and other living arrangements?
• Nickerson conducted this study during a primary. But what about during higher-salience elections?
• Turnout might be contagious, but what about other behaviors, like volunteering, donating, or even vote choice?

Nickerson’s paper uses the best of methods to make a fascinating contribution to the literature. Still, I would ask just a couple more questions.

First, Nickerson does not randomly select which member of each household receives the message; instead, the message goes to whomever answers the door. It seems plausible that the person more likely to answer the door might differ from the person who does not. Might the effect have been (slightly) different if the message were delivered to the second person instead of the first?

Second, what causes this contagion? Nickerson mentions two possible reasons, the lowered costs of voting (sharing a ride to the polls) and the social pressure to conform (see Gerber, Green, and Larimer 2008). My hunch is that it’s the latter; it’s easy to ignore your civic duty to vote when your spouse also ignores it, but if your spouse bothers to vote, the situation changes. It might be nice to see further research looking specifically at how social pressures and civic duty operate within the family.