An estimation of the strategic votes transferred from the United Left to the Socialist Party in the Spanish general elections from 2000 to 2008

In this paper we use the method of counterfactual simulation to estimate the number of strategic votes transferred from the United Left (IU) to the Socialist Party (PSOE) in the last three Spanish general elections. The strategic voters we refer to a re those who, in spite of IU being their first political preference, voted for the PSOE in order to attain representation benefits. The counterfactual simulation procedure is used to examine how the predicted individual probability of voting for a party changes when the strategic incentives at constituency level are removed. Our results lend support to the hypothesis that IU's electoral and parliamentary collapse was due in no small measure to the strategic behavior of its followers.