Sunday, October 28, 2012

2012 Polls: When Is A Lead Really A Lead?

With the campaign between President Barack Obama and Republican presidential nominee Mitt Romney entering its final 10 days, interest in the pre-election polls is at an all-time high, with at least one high-profile pundit confessing to being a "pollaholic."

But for all the dissection of polling methods, one question continues to be a particular source of confusion: When is a lead really a lead?

The aggregate pattern of the national tracking polls continues to indicate a very close race for the national popular vote, with mostly random variation from day to day. The table below, which -- as of this writing -- shows the most recent release of seven daily tracking polls plus two more national surveys fielded in the last week, shows everything from a 2-point Obama edge to a 5-point Romney advantage (for the most recent updates of the daily trackers, see the HuffPost Pollster national tracking chart).

2012-10-27-nationalpolls.png
Keep in mind that since the national polls report margins of sampling error ranging from +/- 2 to +/- 4 on the estimate of support for each candidate, neither candidate's nominal leads on any of these polls can be considered statistically significant.

Seemingly non-random patterns sometimes appear in these daily numbers that may may seem to momentarily favor either Obama or Romney, but since early October these fluctuations have all proved to be little more than random noise. As is more typical, the most recent daily tracker updates, as of this writing, show no consistent pattern either way, with two ticking in Obama's favor, one in Romney's favor and four unchanged.
Since the contest will ultimately be decided by the electoral college votes determined by separate contests in individual states, many ask -- with good reason -- why we follow national polls at all? The most important reason is that the daily tracking surveys now interview more than 2,000 likely voters a day. They may differ on the level of support they measure for each candidate, but if a consistent trend emerges over the next 10 days, these surveys will likely detect it first.  POST

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