PRINCETON, NJ -- Gallup Poll Daily tracking shows that Hillary Clinton now receives 46% of the support of Democrats nationally, compared to 45% for Barack Obama, marking the first time Obama has not led in Gallup's daily tracking since March 18-20.

These results are based on interviewing conducted April 16-18, including two days of interviewing after the contentious Wednesday night debate in Philadelphia and the media focus that followed. Support for Hillary Clinton has been significantly higher in both of these post-debate nights of interviewing than in recent weeks. The two Democratic candidates are now engaged in intensive campaigning leading up to Tuesday's Pennsylvania primary and are under a continual and hot media spotlight, increasing the chances for change in the views of Democrats in the days ahead. (To view the complete trend since Jan. 3, 2008, click here.)

There has been no change in the general election trial heats, with Obama's margin over Republican John McCain at 45% to 44% among registered voters nationally, and Clinton's margin at 46% to 44%. -- Frank Newport

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 April 16-18, 2008. For results based on this sample of 1,241 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 April 14-18, 2008. For results based on this sample of 4,392 registered voters, the maximum margin of sampling error is ±2 percentage points.

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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