PRINCETON, NJ -- With exactly three weeks remaining before Election Day, Barack Obama leads John McCain in the presidential preferences of registered voters by nine percentage points, 51% to 42%.

Gallup is also looking at the race according to two likely voter scenarios. One, the traditional Gallup approach, takes into account voters' intentions to vote in the current election as well as their self-reported voting history. Among this group, Obama leads McCain by six points, 51% to 45%. The other approach uses only voters' self-professed likelihood to vote in 2008, but does not factor in whether respondents have voted in past elections. Among this expanded group, Obama leads by 10 points, 53% to 43%.

As noted in Tuesday's report, between 50% and 52% of registered voters have favored Obama in each Gallup Poll Daily tracking report since Oct. 4. Support for McCain has been a steady 41% to 43% across the same time period. Thus, although the gap between the two candidates has varied from seven to 11 points in recent days, the preferences of registered voters have, in fact, been quite stable, with Obama averaging a nine-point lead. (To view the complete trend since March 7, 2008, click here.)

Today's three-day rolling average, based on interviews conducted Oct. 11-13, includes two days of interviewing following last week's steep drop in the stock market, and interviewing on Monday night after the Dow Jones Industrial Average surged a record 936 points. It is unclear from the individual days' tracking results whether these contrasting events have had any immediate impact on voter preferences. -- Lydia Saad

(Click here to see how the race currently breaks down by demographic subgroup.)

Survey Methods

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. 11-13, 2008. For results based on this sample of 2,793 registered voters, the maximum margin of sampling error is ±2 percentage points.

For results based on the sample of 2,140 "traditional" likely voters (based on the model taking into account current voting intention and past voting behavior), the maximum margin of sampling error is ±2 percentage points.

For results based on the sample of 2,289 more broadly defined likely voters (based on the model taking into account current voting intention only), the maximum margin of sampling error is ±2 percentage points.

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.