Sunday, November 4, 2012

Pew and the Polling Average

The final Pew poll is out today and it is very, very bad news for Mitt Romney. Obama is up by 3 among likely voters.

The polling averages are always the best indicator of where the race stands, especially relative to any single poll. But the Pew poll does have all the characteristics of a good poll.

1) Pew has a good historical track record
2) Pew has a very big sample; 2,709 likely voters were interviewed
3) Live interviews
4) Large numbers of cell-phone only voters were interviewed

This one poll can be wrong because of sampling error. The margin of error among likely voters is +/- 2.2 points which means the margin between Obama and Romney is highly likely to be within the range of Obama +7.4 and Romney +1.4. So there is room to interpret this poll as consistent with a small lead for Romney. But it is a narrow space.

The possibility of bias exists here too. But Pew's methodology is very, very solid in every way a pollster can control. Romney's hopes increasingly depend upon some "X factor" that pollsters are not currently able to identify.

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