In his campaign for the U.S. presidency from 1975 to 1979, Ronald Reagan delivered over 1000 radio broadcasts. For over 600 of these we have direct evidence of Reagan's authorship. The aim of this study was to determine the authorship of 312 of the broadcasts for which no direct evidence is available. We addressed the prediction problem for speeches delivered in different epochs and we explored a wide range of off-the-shelf classification methods and fully Bayesian generative models. Eventually we produced separate sets of predictions using the most accurate classifiers, based on non-contextual words as well as on semantic features, for the 312 speeches of uncertain authorship. All the predictions agree on 135 of the "unknown" speeches, whereas the fully Bayesian models agree on an additional 154 of them.

The magnitude of the posterior odds of authorship led us to conclude that Ronald Reagan drafted 167 speeches and was aided in the preparation of the remaining 145. Our inferences were not sensitive to "reasonable" variations in the sets of constants underlying the prior distributions, and the cross-validated accuracy of our best fully Bayesian model was above 90 percent in all cases. The agreement of multiple methods for predicting the authorship for the "unknown" speeches reinforced our confidence in the accuracy of our classifications.