WASHINGTON -- Republican challenger Mitt Romney, largely viewed as the winner of the first U.S. presidential debate last week, is now evenly split with Democratic incumbent Barack Obama in voters' support, according to the post-debate Gallup polls released on Monday.

The Gallup daily tracking poll was conducted from Oct. 4 to 6 and had a 3-point margin of error. It showed 47 percent of U.S. registered voters respectively supported Obama or Romney. In the Sept. 30 to Oct. 2 poll, prior to the Oct. 3 night debate, Obama led Romney in five percentage points.

The somewhat subdued incumbent and the generally more aggressive challenger began their first face-to-face debate of this election circle on Oct. 3 at Denver University in Colorado state.

Another Gallup poll conducted between Oct. 4 and 5 found roughly two in three Americans reporting that they watched the Oct. 3 debate, similar to what Gallup measured for each of the three 2008 presidential debates.

Those who viewed the debate overwhelmingly believed Romney did a better job than Obama, by a large margin of 72 percent to 20 percent.

Among the registered voters, Republicans were nearly unanimous in picking Romney as the winner. But even Democrats rated Romney as doing better than Obama, by 49 percent to 39 percent.

Gallup said the 52-point edge for Romney was the largest winning margin measured by the polling firm for a debate. The prior largest margin was 42 points for Bill Clinton in the 1992 town hall debate over George H. W. Bush.

Gallup said the first debate in this election cycle appeared to have affected voters to some degree, although the impact was not strong enough to change the race. The unemployment rate of 7.8 percent released last Friday, the lowest since September 2009 and the first time in nearly four years below 8 percent, may serve to blunt some of Romney's post-debate momentum.