Gallup Daily: Obama Opens Up 16-Point Lead, Biggest Yet Lead is now 55% to 39% over Clinton

PRINCETON, NJ -- Gallup Poll Daily tracking finds Barack Obama with his largest advantage over Hillary Clinton in Democratic voters' nomination preferences thus far, 55% to 39%.

Obama's previous largest lead was 11 percentage points, in May 15-17 and April 12-14 polling. His widening lead over Clinton has been evident in each of the last three days of tracking, after the two had been more closely matched earlier in the month.

Clinton's largest lead in the Gallup Poll Daily tracking was 20 points in mid-January, when she led Obama 48% to 28% (John Edwards was still in the race at that time). (To view the complete trend since Jan. 3, 2008, click here.)

Tuesday, voters in Kentucky and Oregon will register their preferences for the Democratic nomination. Clinton is expected to win Kentucky and Obama Oregon. There is some speculation that Obama may declare victory given that he is expected to clinch a majority of the delegates available in the state primaries and caucuses (outside of the contested Florida and Michigan primaries). Clinton has vowed to stay in the race until all the primaries and caucuses have been held in early June.

Despite her growing deficit to Obama in the Democratic race, Clinton continues to poll slightly better than Obama in matchups for the general presidential election vs. John McCain. The latest tracking results, based on May 14-18 polling, shows Clinton with a 48% to 44% lead over McCain among registered voters nationwide, while Obama has just a 1-point edge (46% to 45%) over the likely Republican nominee. -- 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 16-18, 2008. For results based on this sample of 1,261 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 14-18, 2008. For results based on this sample of 4,444 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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