Polls in the United States show President Barack Obama has received a modest rise after last week's Democratic national convention.
The latest Gallup poll shows Mr Obama pulling ahead of his Republican rival Mitt Romney by four percentage points.
For weeks, most polls have shown Mr Obama and Mr Romney in a dead heat.
Some 47% of 1457 likely voters surveyed online over the previous four days said they would vote for Mr Obama if the November elections were held that day, compared with 43% for Mr Romney.
Mr Obama also leapfrogged Mr Romney in a separate poll on Friday, with a lead of 46% to 44%.
Mr Romney says Americans should be disappointed with the president's handling of the economy.
