Republican challenger Mitt Romney edged U.S. President Barack Obama among "likely voters" while Obama maintained a marginal lead among registered voters, less than a month ahead of November showdown, according to Gallup' s first national survey on likely voters released Tuesday.

The Gallup's first "likely voters" survey, conducted from Oct. 2-8, found Romney held a slight edge over Obama by 49 percent to 47 percent. However, among registered voters, which Gallup has been tracking all year, the incumbent took 49 percent against the challenger at 46 percent.

"Neither result provides a candidate with a statistically significant lead, but together they do underscore the competitive nature of the election and indicate that Romney at this point benefits from turnout patterns, given the five-point swing in his favor when the transition is made from registered voters to likely voters," Frank Newport, Gallup's Editor-in-Chief, wrote in his analysis.

Newport said the registered voter trends suggest that Romney's initial gains from his strong performance in last week's first presidential debate may not have a long lasting impact while the findings about likely voters suggest Romney at this point appears to have a turnout advantage, meaning that Obama will need to develop a strong lead among all registered voters in order to be assured of winning the actual popular vote.

Asked about Romney's edge among "likely voters," the Obama campaign's spokesperson Jennifer Psaki told reporters that the campaign has been focused on "getting our supporters out" despite "many ups and downs."

"...we are always run this race like we are five points down," said Psaki.

The Gallup's findings about likely voters also echoed another poll released on Monday by Pew Research Center, which showed among likely voters, Romney holds a slight 49 percent to 45 percent edge over Obama.

The Pew poll also found Romney has caught up to tie with Obama in the presidential race among registered voters by 46 percent to 46 percent after trailing by nine points in September.