It’s not often that a pollster admits an error. They deal in such slender differences in figures and pride themselves on keen interpretation. So it is rare and surprising to hear John Zogby, head of the eponymous pollsters, admitting, “This was not Zogby International’s finest hour. “Something, somehow, fell through the cracks,” notwithstanding a defiant denial of culpability on his website the day before. In dispute is a survey complete for Ziegler about how much Obama voters knew about politics, a contribution to a Ziegler documentary movie about how the press swung the presidential election. In brief, Zogby extrapolated how voters came to back Obama based on slender evidence –interviews with just 10 Obama voters. The Wall Street Journal’s numbers guy dissects Zogby’s shaky reasoning.