Colorado Democrat Mark Udall has endured millions of dollars of abuse in the form of negative advertising, but he could be feeling the effects for the first time. A new poll conducted by Mason-Dixon for the Denver Post surveyed 625 likely voters between 9/29-10/1 for a margin of error of +/- 4%. Udall and ex-Rep. Bob Schaffer were tested.

General Election Matchup
Udall.........43 (-4 from last, 8/15)
Schaffer......38 (+1)

The negative tone of the campaign has driven Udall's unfavorable ratings up to 26%, a three-point rise in a month. But the tone has had a more dramatic effect on Schaffer's popularity, as 43% of voters see him unfavorably. That's an 18-point rise in just six weeks.