En las próximas semanas nos familiarizaremos con el concepto "convention bounce" -o bump. Se llama así al avance que un candidato logra en los sondeos sobre intención de voto como consecuencia de una Convención bien recibida por el público. En el gráfico superior podéis observar los bounces de los últimos cuarenta años -con el rojo republicano y el azul demócrata. Ojo, el gráfico no muestra la subida del día siguiente, sino un contraste entre la media de la semana anterior a la apertura de la Convención, y la media de los siete días posteriores a la clausura de la Convención.
Gracias a la buena organización de las Convenciones modernas, los candidatos siempre tienden a salir reforzados. Aunque a veces de forma desigual. En Election '08: Data and Pictures nos dan algunas claves para reconocer el fenómeno.
(...) The first thing to note is that there is a lot of variation in convention bumps. Fortunately, as I showed in Do Campaigns Matter?, there is a systematic component to that variation. Two things in particular seem to drive the size of the bumps. First, candidates who are running ahead of where they "should" be (based on the expected election outcome) tend to get smaller bumps, and those running behind their expected level of support get larger bumps. In this way, the conventions help bring the public closer to the expected outcome and help to make elections more predictable.
The perfect example of this phenomenon is the 1964 conventions. Goldwater got a huge bump, in part because he was running 16 points behind his expected vote share, and Johnson got no bump, in part because he was running 6 points above his expected vote share. Likewise, Al Gore was running well behind his expected level of support in 2000 and got a substantial bump, while George W. Bush was running ahead of his expected level in the same year and received a rather modest bump. (...)
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