Kernell: Explaining presidential popularity
Disclaimer. Don't rely on these old notes in lieu of reading the literature, but they can jog your memory. As a grad student long ago, my peers and I collaborated to write and exchange summaries of political science research. I posted them to a wiki-style website. "Wikisum" is now dead but archived here. I cannot vouch for these notes' accuracy, nor can I say who wrote them.
Kernell. 1978. Explaining presidential popularity: How Ad Hoc Theorizing, Misplaced Emphasis, and Insufficient Car. American Political Science Review 72: 506-22.
Main Argument: Time is Not a Variable
Prior to this paper, the conventional wisdom on presidential popularity was that presidents inexorably become less popular over time. Time was given theoretical meaning and was used as an explanatory variable. Kernell argues that time cannot be used as an explanatory variable. Instead, it should be used as a diagnostic to ensure that all trend-producing variables have been identified.
Mueller's Argument
In an analysis of presidential popularity from Truman to Johnson, Mueller used time as the chief explanatory variable of decreasing presidential popularity. Borrowing from Downs, he argues that the president frequently loses public support even when he follows the majority opinion of the public due to the "coalition-of-minorities" effect.
- Mueller reported a linear relationship between time and presidential popularity.
- Mueller, controlling for an overall downward trend in Johnson's presidency, claimed that the Vietnam War had no independent impact on presidential popularity
Kernell's Hypotheses:
- Short-term changes in presidential popularity are related to real events and conditions
- Presidential popularity responds slowly to environmental changes; the president's current popularity reflects the level of approval during the previous month(s).
How to Measure Presidential Popularity: Mueller vs Kernell
Chronic problems: Korea, Vietnam, Watergate
- Mueller measures chronic problems as either "on" or "off". This dichotomous index assumes that the impact of these events was the same from beginning to end.
- Kernell measures chronic problems as a function of specific indicators. For example, he used the number of casualties as an indicator for the Korean War.
- Chronic problems contribute independently to short term fluctuations in presidential popularity
The Economy: Unemployment Rate, Consumer Price Index
- Mueller measured the two indices by percent change from the start of a President's term
- Kernell measured the two indices by percent change over 6 month intervals.
- Inflation is a particularly good indicator of public opinion
- Unemployment is not a good indicator of public opinion, possibly due to its negative correlations with war.
Short term surges: "rallies behind the flag"
- Mueller estimated lengths of time between rally points, beginning each new Presidential term as a automatic rally point
- Kernell makes rally points have decreasing values over a 5 month period, at which point the rally variable is scored as zero
- When inauguration rally points are eliminated, the correlation between rallies and popularity becomes negative under the Johnson, Truman, and Eisenhower presidencies and are only benignly positive for Kennedy and Nixon.
- Rally points only explain popularity surges in the first 6 months of a President's term.
