A few days ago, I proclaimed that I expected the national polling margin to drop to 4-5%, and then stabilize. So far, my prediction is a little off, as the now eight tracking polls show a slightly larger, and growing, margin for Obama:
Complete Tracking poll average
Org
Obama
McCain
ABC
53%
44%
Gallup*
51%
44%
GWU
49%
45%
Hotline
47%
42%
Rasmussen
50%
46%
R2000
50%
42%
TIPP
46.7%
41.4%
Zogby
49.8%
44.5%
Mean
49.6%
43.6%
* = Gallup is an average of their expanded and traditional likely voter models
So, right now Obama's margin appears to be about 6.0%, a number with which every polling aggregation site comes with a couple tenths of a percent. So, at least for now, it turns out I was wrong about how much Obama's lead would drop. That's cool.
However, I still think that there is a good reason to expect the final polling margin to be 4%. The theory goes like this: in presidential elections, the average poll margin during the campaign equals the final poll margin at the end of the campaign. So far in this campaign, the all-time average has been Obama by 4%. As such, I predict it as the final margin.
The reason is that, since Obama clinched the nomination on June 3rd, the average polling margin appears incredibly stable to me, with only occasional major events temporarily changing the margin. And, according to an email I received to from Charles Franklin of Pollster.com, check out the average polling margins in from the start of June through Election Day in 2000, 2004 and 2008:
2000: Bush +2.4%
2004: Bush +1.4%
2008 (so far): Obama +3.8%
Now, click here to compare the final polling margin in 2000 and 2004 to the average polling margin in both elections. As you can see, the final polling margin in both elections was identical to the average polling margin from June through Election Day. The differences are, at most, one or two tenths of a percent.
My theory is that virtually everyone knows who they are going to vote for in a presidential election as far back as June, and that elections in our contemporary political environment are only altered by major events like conventions or, in our case, a financial crisis. Undecideds make up a very small percentage of hte electorate, and so much money is spent wooing them on both sides, that neither group can gain much advantage.
This year, I see 4% as the likely final polling margin, given that has been the average margin along the way. Now, that doesn't mean the final voting margin will equal that number, as both 2000 and 2004 deviated more than 1% from their final margins (about 1.1% in 2004, and about 3.0% in 2000). However, 4% should be enough for Obama to win in really any scenario you can dig up from that point.
Now, this isn't exactly a well-tested theory, but I thought I would throw it out there. I won't be surprised if the final polling margin tightens to around 4%, but hat Obama will still win. In case the polls do tighten toward the end, at least I can use this theory as a security blanket. The average poll margin equals the final poll margin.
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