WASHINGTON — Senator McCain has taken a modest lead over Senator Obama entering the final seven weeks of their presidential contest, buoyed by decisive advantages among suburban and working-class whites and a huge edge in how people rate each candidate’s experience, a poll showed today.

Mr. McCain has had some success parrying his Democratic opponent’s efforts to tie him to the deeply unpopular President Bush, according to the AP-GfK poll of likely voters. Half say they believe the Arizona senator would chart a different path from Bush.

The survey has plenty of positive signs for Mr. Obama as well. The Illinois senator is generally doing about as well with whites as Democrat John Kerry did in his losing but close 2004 race against Bush. Mr. Obama has an 18-percentage-point lead over Mr. McCain among voters who look more to a candidate’s values and views than experience, and a modest advantage in the number of supporters who say they will definitely vote for their candidate.

Even so, the survey — conducted after both parties staged their conventions and picked their vice presidential candidates — conforms with others that have shown the Republicans grabbing the momentum after a summer in which Obama had steadily maintained a slim lead.

“My heart sort of runs with McCain and my mind probably tends to run toward Obama,” said David Scorup, 58, a county government official in Othello, Wash., who said he is leaning toward McCain. “I think I resonate more with McCain.”