PRINCETON, NJ -- Barack Obama holds a slight advantage over John McCain, 47% to 44%, in the latest Gallup Poll Daily tracking update of general election preferences among registered voters.

Obama's three percentage point advantage is within the poll's margin of error. He has improved his positioning relative to McCain in the past week, when he trailed McCain by as many as three points. In general, the matchup of the likely nominees has been close since Gallup began tracking it in mid-March.

In a hypothetical matchup of Hillary Clinton and McCain, Clinton holds a 4-point lead over McCain, 48% to 44%.

Obama holds a double-digit lead over Clinton for a fourth consecutive day in national Democratic voters' nomination preferences, 53% to 42%.

As the primary and caucus season winds down and his nomination appears increasingly likely, Obama has in recent days enjoyed his strongest showing in Gallup Poll Daily tracking. While he also held double-digit leads at earlier points in the campaign, he has not been able to sustain a lead of that size until now. (To view the complete trend since Jan. 3, 2008, click here.)

On Tuesday, Clinton won a resounding victory in the Kentucky primary while Obama prevailed in the Oregon primary. Most of the interviews in the current tracking results were collected before the outcomes of those contests were known. -- Jeff Jones

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 Democratic nomination results are based on combined data from May 18-20, 2008. For results based on this sample of 1,278 Democratic and Democratic-leaning voters, the maximum margin of sampling error is ±3 percentage points.

The general election results are based on combined data from May 16-20, 2008. For results based on this sample of 4,465 registered voters, the maximum margin of sampling error is ±2 percentage points.

Interviews are conducted with respondents on land-line telephones (for respondents with a land-line 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.

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