WASHINGTON: For the first time since April, US President Barack Obama has opened up a sustained lead over presumptive Republican nominee Mitt Romney.

According to the Gallup Poll, Obama leads with 48 percent over Romney at 44 percent, which is the sixth consecutive day in which the poll has shown him lead.

Obama's lead comes after almost two months in which the two candidates were essentially tied in the poll's results, Los Angeles Times reports.

The uptick for Obama started before the Supreme Court's ruling upholding most parts of Obama's healthcare act.

The ruling, itself, does not appear to have had an impact on the shape of the race.

Democratic strategists believe that the Obama campaign's repeated attacks on Romney's business record, particularly the involvement of his company, Bain Capital, in "offshoring" of jobs, has begun to connect with voters.

The results are particularly notable because many polling analysts believe that Gallup's methods for analyzing its surveys slightly under-represents the number of minority voters and, therefore, understates Obama's support by a couple of points.

Several recent state-by-state polls also have showed results consistent with a small increase in Obama's support.