The issue-index model, developed by PollyVote team members Andreas Graefe and Scott Armstrong, predicts the election outcome based on information about how voters expect the candidates to handle the issues. This model is based on the assumption that voters select the candidate they expect to perform best in handling the issues. Thus, it is assumed that, for the voter, it is not primarily important how the candidates intend to solve the problems or what policies they promise to pursue. The voters simply want the problems to be solved.
The table to the left shows voter support for the Democrats and Republicans in handling the issues. If a party’s value for a particular issue is above 50, this means that voters expect that party to do a better job in handling that issue. The complete polling data for this table can be found here.
The percentage of issues (
I) for which voters favor the incumbent party’s candidate is then used as the single predictor variable in a simple linear regression model to predict the national two-party popular vote. The resulting vote equation, which was derived from data on the eleven elections from 1972 to 2012, reads as:
V = 41.8 + 18.0 *
That is, the issue-issue model predicts that an incumbent would start with 41.8% of the vote, plus a share depending on
I went up by 10 percentage points, the incumbent’s vote share would go up by 1.8 percentage points.
Graefe, A., & Armstrong, J. S. (2013). Forecasting elections from voters‘ perceptions of candidates‘ ability to handle issues. Journal of Behavioral Decision Making, 26(3), 295-303.