The Democratic incumbent leads Romney among registered voters by 48 percent to 44 percent, a slight reduction from his 49 percent to 43 percent lead in July.

But other findings show that Democratic attacks have continued to damage his personal reputation, while his new running mate Paul Ryan has elevated a debate over Medicare that so far works to the disadvantage of the Republican ticket. (Related: Ryan's Way: How He Would Change Medicare.)

“Mitt Romney is sliding in the wrong direction,” said Democratic pollster Peter Hart, who conducts the Journal/NBC survey with his Republican counterpart Bill McInturff. “As the debate shifts away from being solely about jobs, Romney’s position weakens.”

Though a sour public mood and weak ratings on the economy continue to weigh on the president, Hart said Ryan’s identification with far-reaching changes to the popular Medicare program has created a counterpoint that benefits Democrats.

“This election has moved from a referendum (on the economy) to a choice election, “ he said. “The Medicare issue gives (Obama) a hammer he didn’t have before now.”

Obama’s lackluster job approval rating, 48 percent, matches the proportion of voters who have a favorable personal impression of him.

Some 43 percent regard him unfavorably.

But Romney’s 44 percent unfavorable rating — his highest of the campaign — exceeds his 38 percent favorable rating. That reflects the unprecedentedly heavy investment Obama and his Democratic allies have made in sullying the former Massachusetts governor’s reputation this summer.