Democrats continued to support Obama and their approval rating actually went up a point in the first eight days of July, to 90 percent, compared to the June average, the poll found. Republican support inched down 2 points to 23 percent.
But 53 percent of independents said in July they approve of Obama's performance, a 6-point drop from June. Overall, 58 percent of those polled had a favorable view of Obama, compared to 61 percent in June.
Obama's biggest loss in standing since his inauguration has been with Republicans, who gave him a 40 percent approval rating in late January.
Frank Newport, the Gallup Organization editor in chief, said most presidents lose ground in the first summer of their election as their honeymoon period with the voters comes to an end.
"What happens from this point, however, on is highly unpredictable," Newport said.
Gallup polled 3,703 adults by telephone in early July. The results have a 2 percentage point margin of error. Monthly polls survey about 15,000 adults with a 1 percentage point margin of error.