How reliable are political polls?
When Bill Fazio read his morning Chronicle late last October, he had every reason to feel good. The newspapers poll of likely voters showed him leading Terrence Hallinan in the San Francisco district attorneys race by 10 percentage points just 10 days before the election. With a margin of error of plus or minus 4 points, the poll showed him ahead even if all the error favored his opponent. But on election day, Hallinan edged Fazio, setting up a run-off election. Not to worry. Ten days before the run-off, a second Chronicle poll showed Fazio had increased his lead to 18 percentage points. The margin of error was again +/- 4 points. If the poll was correct, on December 4 Fazio was comfortably aheadat least by 14 points and perhaps by as many as 22. But on December 14, Hallinan won again. Either the poll was much further off than its margin of error, or there was a substantial and late surge for Hallinan. The Chronicles pollster, Cheryl Katz, director of Baldassare Associates, argues that
