PRINCETON, NJ — The gap between Barack Obama and John McCain in Gallup Poll Daily tracking from Saturday through Monday has narrowed slightly, and Obama is now at 49% of the vote to 47% for McCain among likely voters using Gallup’s traditional model, and at 51% to 44% using Gallup’s expanded model.

Both candidates continued vigorous campaigning on Monday. One forthcoming event with the potential to affect voter sentiments is a 30-minute Barack Obama paid program, for which his campaign has purchased time on Wednesday night on a number of national broadcast and cable television networks.

The two percentage point margin for Obama over McCain in today’s traditional likely voters result, based on Gallup Poll Daily tracking from Oct. 25-27, is not the first time the race has been this close; it matches the two-point Obama margin that held for three straight reporting periods spanning Oct. 13 -17, a week and a half ago. The traditional model assumes that turnout will follow the patterns of past elections, in which both current interest in the election and past voting behavior are predictors of actual voting.

Obama’s seven-point lead among expanded likely voters, based on a model which makes no assumptions about turnout based on past voting history, is fairly typical of what has been measured over the last two weeks, although slightly narrowed from the last two days’ reports. Obama’s lowest margin among this expanded group was four points, measured on Oct. 15-17.

Obama is also now at a seven-point margin over McCain among registered voters, 50% to 43%. (To view the complete registered voter trend since March 7, 2008, click here.) — Frank Newport

(Click here to see how the race currently breaks down by demographic subgroup.)