A new poll on the state of the U.S. Senate race in Colorado, released Thursday by the campaign of Democrat Mark Udall shows the lawmaker leading Republican opponent Bob Schaffer by 11 percentage points.

That's close to the largest lead of either of the U.S. Senate candidates seen in any poll of the race since pollsters started surveying the race a year ago.

Recent polls by the Schaffer campaign and the National Republican Senatorial Committee showed the race within the margin of error.

Udall's poll, conducted Sept. 7-9 among 752 likely Colorado voters by Udall's pollster, Harstad Strategic Research, Inc., has a margin of error of +/- 3.6 percent.

Of those surveyed, 37 percent identified themselves as Republicans; 31 percent were self-described Democrats, while 32 percent said they were unaffiliated, according to Udall spokesperson Tara Trujillo.

The Udall campaign hailed the poll results in a press release, saying a multimillion-dollar ad campaign against him by Schaffer's campaign and 527 groups has failed to sway voters.

Indeed, the latest poll found that voter preference for Udall on the issue of energy has increased over the past month.

The new poll found 44 percent of those surveyed preferred Udall's approach to energy, compared to 28 percent who favored Schaffer's views. That 16-point margin is up from the results of an internal Udall campaign poll taken last month showing Udall with an 11-point advantage on the energy issue.

"These results indicate that the attack campaign being waged by several out-of-state groups on Bob Schaffer's behalf has been strikingly ineffective so far," said Paul Harstad, CEO of Harstad Strategic Research, in the release. "In fact, to the contrary, Mark Udall's position has actually strengthened on the exact issues these ads have sought to attack him on."

But Schaffer manager Dick Wadhams called the numbers "fictitious," pointing to the Schaffer campaign and NRSC polls showing the race in a dead heat.

"This race, in reality, it is deadlocked," Wadhams said. "And if they want to believe their fanciful numbers, I invite them to do so."

American Constitution Party candidate Douglas Dayhorse Campbell was favored by 3 percent of those polled; Green Party candidate Bob Kinsey polled 2 percent.

CORRECTION 12:46 P.M. 9/11/08: The article initially stated, in error, that the 11-point lead in Udall's new poll is the largest lead by either candidate of any poll taken of the race. In March, a McLaughlin & Associates poll showed Udall with a 12-pont lead.