U.S. Republican presidential candidate John McCain (L) and U.S. Democratic presidential candidate Barack Obama meet as they walked onstage during the first U.S. presidential debate at the University of Mississippi in Oxford, Mississippi, September 26, 2008.

WASHINGTON, Oct. 6 (Xinhua) -- U.S. Democratic presidential candidate Barack Obama is moving further ahead in all national polls Monday in the wake of economic downturn and financial crisis

The latest CNN survey found Obama now leads McCain 53 to 45 percent, doubling the 4-point lead Obama held in the last CNN poll in mid-September.

The Gallup daily tracking poll also show Obama leads by 8 percent, with 50 percent of the respondents supporting him and 42 percent supporting McCain.

In all other national polls, Obama's leading margins range from6 to 8 percent.

Pollesters said the Obama's gains could be attributed to the financial turmoil, record-low approval ratings for Republican President George W. Bush and a drop in the public's perception of Republican presidential candidate John McCain's running mate Sara Palin.