PRINCETON, NJ -- Barack Obama begins the final week of the campaign with an advantage over John McCain in both Gallup likely voter models, up by 49% to 46% using the traditional model and leading 51% to 44% using an expanded likely voter model.
The current results, based on Gallup Poll Daily tracking from Oct. 26-28, are essentially the same as in Tuesday's report, and show a slightly closer race than Gallup tracking had reported prior to that.
Tonight, Barack Obama is using some of his record campaign funds to air a 30-minute campaign advertisement on most major television networks. Any possible impact of the ad on voter preferences will be apparent in the coming days. Gallup has only found about 4% of likely voters to be truly undecided at this late stage of the campaign, in that they do not express a preference or leaning for Obama, McCain, nor some other candidate.
Obama has a slightly larger lead among the pool of all registered voters, currently at 51% to 42%. These percentages have been stable throughout October, and the current figures precisely match the average for the month to date. (To view the complete trend since March 7, 2008, click here.)
(Click here to see how the race currently breaks down by demographic subgroup.)
For the Gallup Poll Daily tracking survey, Gallup is interviewing no fewer than 1,000 U.S. adults nationwide each day during 2008.
The general-election results are based on combined data from October 26-28, 2008. For results based on this sample of 2,789 registered voters, the maximum margin of sampling error is ±2 percentage points.
For results based on the sample of 2,435 "traditional" likely voters (based on the model taking into account current voting intentions and self-reported past voting behavior), the maximum margin of sampling error is ±3 percentage points. The traditional likely voter model assumes a turnout of 60% of national adults. The likely voter sample is weighted to match this assumption, so the weighted sample size is 1,812.
For results based on the sample of 2,409 "expanded" likely voters (based on the model taking into account current voting intentions only), the maximum margin of sampling error is ±2 percentage points. The expanded likely voter model does not make any assumptions about turnout level.
Interviews are conducted with respondents on landline telephones (for respondents with a landline telephone) and cellular phones (for respondents who are cell phone only).
In addition to sampling error, question wording and practical difficulties in conducting surveys can introduce error or bias into the findings of public opinion polls.