There’s no reason a smaller sample size should be biased one way or the other. The chances are very small that all the small sample sized polls are leaning more towards Obama just by chance. More likely it has something to do with methodology. For example, are the polls favoring Obama weighted for a Dem turnout similar to 2008?
>> There’s no reason a smaller sample size should be biased one way or the other <<
Agreed that there “should” be no difference in the bias between a large sample and a small sample. But over the past couple of weeks that I’ve been following the RCP averages, there does seem to be a remarkable pattern where the small-sample polls tend to favor Øbama and the large-sample polls tend to favor Romney.
My hypothesis to explain this pattern is that the small-sample polls are mainly low-budget undertakings where the poll takers and/or their financial sponsors have decided it would be too expensive to use “more representative” polling techniques, meaning that they tend toward having samples that over-represent Ø-leaning LV’s.