The Gallup generic Congressional preference poll (R+15%) has drawn notice, including from ostensibly statistics-savvy poll geeks. It’s unclear why since individual data points always vary more than averages. Then again, as the saying goes, if it bleeds it leads. But there’s something more surprising.
In addition to random variation, Democrats seem to have a hidden advantage relative to national House preference polls, which are averaging R+7%. But district-level polls (which indicate 230R-205D) are said to be equivalent to R+4%. Can both be right? District polls tend to be concentrated in key districts. If the Republicans’ final House seat advantage matches district polls (a majority of 25 seats), it’s an underperformance relative to national surveys. Lucky for the Democrats – though not lucky enough. Maybe they have a better machine / strategy. Or maybe it’s systematic error when the question is asked generically.
Based on the excellent performance of direct polls in 2004/2006/2008, the hypothesis to beat is listed above. If the House is outside [228, 232] R or the Senate is outside [50, 52] D, then I’ll want to know why.