PRINCETON, NJ -- Regardless of the predictors used to identify likely voters, the conclusion is the same -- Barack Obama maintains a significant lead over John McCain in the latest Gallup Poll Daily tracking presidential election trial heat.
Today's results are based on Oct. 19-21 interviewing, and show Obama with a 50% to 45% lead over McCain when likely voters are defined using Gallup's traditional likely voter model, and with a 52% to 44% lead using an expanded model.
The traditional model assumes that those who express a strong intention to vote this year and who have voted often in the past will vote this year. The expanded model does not rely on past voting behavior as a predictor of turnout this year, and thus defines likely voters as those who express a strong intention to vote this year.
The likely voter estimates for each candidate have generally been stable since Gallup began measuring them about two weeks ago. Obama's support has ranged between 49% and 51% using the traditional model and a slightly higher 50% to 53% using the expanded model. McCain's support has ranged between 44% and 47% in the traditional model and 42% to 46% in the expanded model.
Among all Americans who are registered to vote, Obama currently holds a 51% to 42% lead, which matches his average for October to date.
Obama has been ahead among registered voters throughout much of the campaign, except for a brief period in March after McCain clinched the Republican presidential nomination, and a second, brief period in early September following the Republican National Convention that ended around the time the financial crisis intensified. (To view the complete trend since March 7, 2008, click here.) -- Jeff Jones
(Click here to see how the race 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 Oct. 19-21, 2008. For results based on this sample of 2,799 registered voters, the maximum margin of sampling error is ±2 percentage points.
For results based on the sample of 2,420 "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 1,822.
For results based on the sample of 2,331 "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.