The Gallup Poll Daily's tracking, conducted June 12-14, found 44 percent of national registered voters favor Obama, while 42 percent support McCain.

Since Obama's lead falls within the poll's two-point margin of error, he and McCain are statistically tied.

Obama had led by as many as 7 percentage points in days immediately following New York Sen. Hillary Clinton's exit from the Democratic nominating contest.

The Gallup poll also found that 14 percent of the 2,828 voters surveyed do not favor either major-party candidate.