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The Cell-Phone-Only Difference: A Final Look

11/02/2008 11:58 pm 23:58:32 | Updated May 25, 2011

A little over a week ago, I posted two different national trend estimates: one for pollsters who were reaching cell-phone-only (CPO) respondents by calling cell phones in addition to landlines and one for those who were only calling landlines. At the time, Obama's lead in the trend of pollsters accounting for CPOs was about 3% wider than among those who were only calling landlines.

Here are the two different trend estimates as they stand on the even on eve of the election.

National Trend Estimate for Pollsters Reaching Cell Phone Only Respondents

National Trend Estimate for Pollsters not Reaching Cell phone Only Respondents

If anything, the difference between the two trends is greater now than it was a week and a half ago. As of Monday morning, Obama's lead was 4.2% larger in the national trend accounting for the CPO population than it was among the landline-only polls. In addition, while the landline-only polls are showing some late tightening in the national trend, the surveys reaching CPO respondents do not show any such tightening.

While many of the major national polling firms have made a great effort to include CPOs in their polling this fall, it is important to keep in mind that most of the state-level surveys fail to reach CPOs. Thus, there is a possibility that the state trend estimates may be under-estimating Obama's support. What happens if we try to account for the CPO effect in the statewide trends?

The three charts below show Obama's margin in the states currently classified as leaning or toss up on the Pollster.com map. The first chart shows the Obama margins according to the Pollster.com trend estimates as of Monday morning. The second chart makes a conservative CPO adjustment by adding 2% to Obama's margin in each state. And the third chart makes a 4% adjustment to the CPO to mimic the current difference we see between the two national trends.

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cpo2.PNG

cpo3.PNG

If you make no CPO adjustment and give each state to the candidate currently leading, Obama wins 367 electoral votes, narrowly losing Indiana, Montana, and Georgia and narrowly winning North Carolina and Missouri. Making a conservative CPO adjustment by adding 2% to Obama's margin in each state pushes Indiana and Montana into Obama's column, giving him 381 electoral votes. Finally, if you make a 4% CPO adjustment to Obama's margins in each state (based on the differences in the national trends), Georgia suddenly shifts into Obama's column, giving him 396 electoral votes. Of course, it is important to keep in mind that the cell phone only population is not evenly distributed across the 50 states so not all states will be affected in the same way. But if you believe that there is a cell phone only effect that the state trends are not capturing, then states like Virginia, Nevada, and Ohio are not even that close right now and Obama has a good chance of winning in Indiana, Montana, Georgia, and possibly even Arizona.

Tomorrow night, we will have a better sense of how much a difference the CPO population has made in polling this race. Which of the national trends presented here comes closer to pegging the final popular vote tally? Does Obama win some of the states where the polls show him behind by a few percentage points? The bigger the Obama margin in the national vote and electoral college, the more likely that some pollsters missed some of his support by failing to reach the CPO population.

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