But with Ann Romney, Mr. Romney’s wife, taking the stage on Tuesday night, the Republican gathering will be as much about presenting Mr. Romney as a warm-blooded family man who understands the tribulations of everyday people. The campaign, after spending months arguing that the family’s Mormon faith was off limits, invited speakers from Mr. Romney’s church to testify how he had helped them when they were in need.

Those concurrent themes reflect a realization by strategists inside the Romney campaign and its allies at outside groups in recent weeks: Republicans need to do more than critique Mr. Obama’s economic record for Mr. Romney to win. With the race entering its final, decisive phase, strategists on both sides agree that Mr. Obama maintains a razor-thin edge.

That, several Republican officials said in interviews, is the result of a stubborn affinity for Mr. Obama among key swing voters who otherwise say they are disappointed in his job performance — a dynamic the Romney campaign and its allies are seeking to change.

Mr. Law said his group, Crossroads, had reserved roughly $35 million in advertising for the rest of the campaign and planned to spend more on efforts speaking to their other perception, that Mr. Obama had not been able to deliver.

“These folks know they are not happy with what Obama has done, but they are struggling between, ‘I voted for him, I liked him, but he’s not getting the job done,’ ” said Carl Forti, political director for American Crossroads. “That’s where Mitt needs to take advantage.”

But, strategists acknowledge, Mr. Romney still has work to do before those critical swing voters will view him as that alternative, particularly with polls showing that voters see him as less attuned to their needs and values than Mr. Obama is. While he hopes to improve his standing among women, strategists say Mr. Romney’s chances hinge to a large degree on running up his edge among white voters who do not yet trust Mr. Romney.

“Right now the perceptions of him are allowing Barack Obama to stay in this race and keep a slight lead in spite of all the environmental factors that lead you to think he should be gone,” said Matthew Dowd, a pollster for George W. Bush’s campaigns. “If he can change perceptions about himself, then the environment takes hold, and if the environment takes hold, they win.”