A Denver Post/Mason-Dixon poll released Sunday shows Democratic U.S. Senate nominee Mark Udall leading Republican opponent Bob Schaffer 47 percent to 43 percent.

That 4-point lead is within the poll's margin of error and is dramatically smaller than most other poll results the past month that have shown Udall with a double-digit lead.

However, the survey showed Udall with an impressive 19-point lead among independent voters. And Mason-Dixon pollster Brad Coker, who conducted the survey, said the basic dynamics of the race - which favor Udall -- are still the same.

"Schaffer's only gains have been with Republicans. He hasn't moved Democrats or done better with independents," Coker told the Post. "Basically, Udall is still ahead and Schaffer's battle is still uphill."

The poll found more voters still view Schaffer negatively than positively; the reverse is true for Udall, the Post reported, though no specific favorable/unfavorable numbers were released.

Three percent of those surveyed favored Green Party nominee Bob Kinsey; 7 percent were undecided.

The poll, conducted Oct. 28-29 among 625 registered Colorado voters, has a margin of error of +/- 4 percentage points.