This paper uses a pre-election poll conducted by the Centro de Investigaciones Sociológicas (CIS)1 to demonstrate how election forecasts in Spain could be improved by using two modes of data collection. As a result of the differences in coverage and nonresponse across modes, the face-to-face and computer-assisted telephone interviewing (CATI) samples provide distributions of some of the population attributes that balance each other out resulting in a better performance of the combined sample than either sample considered separately. The full results of this research appear in Díaz de Rada (2010).