The Gallup Poll Daily tracking of registered voters released Thursday indicate the presumptive Democratic presidential nominee dropped from a 47 percent-to-41 percent advantage over his likely Republican challenger during the week of July 21-27 to a 45 percent-to-44 percent edge July 28-Aug. 3.
Voter preferences on an average weekly basis have been stable since early June, the Princeton, N.J., polling agency said. More recently, Gallup Poll Daily tracking reports from Monday-Wednesday have tended to show Obama with a slight lead.
During both periods, Obama maintained broad support among Democrats, liberals, moderates, women, youth, blacks, Hispanics, and several other segments, pollsters said.
McCain maintained strength among men, seniors, whites, conservatives, Protestants and Republicans.
Major subgroups -- including college graduates, political independents and Roman Catholics -- haven't given either candidate a large or consistent backing, the poll said.
For the Gallup Poll Daily tracking survey, at least 1,000 adults nationwide were interviewed each day. The overall margin of error is 1 percentage point. Samplings of subgroups of registered voters had higher margins of error.