Presidential polls differ as election nears

Washington (CNN) -- Two national polls released Monday suggest Republican presidential nominee Mitt Romney got a bounce out of last week's first presidential debate, though they differ on how much of a bump the GOP nominee received after his performance in Denver.

According to a Pew Research Center survey released Monday afternoon, 49% of likely voters say they back Romney, with 45% supporting President Barack Obama. The survey was conducted October 4-7, the four days after last Wednesday's first presidential debate in Denver, Colorado. Romney's four-point advantage is within the survey's sampling error.

In Pew's previous poll, conducted in mid-September, the president had a 51%-43% lead among likely voters.

Meanwhile, Gallup's latest daily tracking poll of registered voters, also released Monday afternoon, indicates the president with a 50%-45% advantage over Romney. The president's edge is within the survey's sampling error. The poll was conducted October 1-7, both before and after the debate.

Early Monday Gallup released a breakdown of its previous tracking poll, which was conducted September 30-October 6. The survey indicated that Obama held a 50%-45% advantage over Romney from September 30-October 2, the three days leading up to last Wednesday's presidential debate, and that Romney and Obama were deadlocked at 47% each in the three days after the debate, from October 4-6.

Responding to the Pew poll, an Obama campaign official pointed to discrepancies in the party identification percentages used in Pew's mid-September poll compared to the poll released Monday.

The earlier survey was composed of 39% Democrats, 29% Republicans and 30% independents, while Monday's poll was comprised of 31% Democrats, 36% Republicans and 30% independents.

"This is far bigger than any one-month change in party ID ever reported by Pew in the past," the Obama campaign official said.

Another representative of the Obama campaign said the "state of the race is what it has been, which is a close and competitive race in key states with a slight lean towards the president."

Meanwhile, a Romney campaign official said the GOP effort was "encouraged by the enthusiasm we are seeing from supporters who are energized, as well as undecided voters who are now giving the Governor a new look." They are "continuing to work hard to bring home persuadable voters," the official said.

The new Gallup Tracking poll questioned approximately 2,200 registered voters nationwide by telephone. The survey's sampling error is plus or minus three percentage points.

The Pew Research center poll questioned 1,112 likely voters by telephone. The survey's sampling error is plus or minus 3.4 percentage points.