Democrat Mark Udall's lead over Republican Bob Schaffer in Colorado’s race for the U.S. Senate has grown slightly over the past month. The latest Rasmussen Reports telephone survey in the state finds Udall ahead 47% to 41%.

When “leaners” are included, the Democrat has a 50% to 42% lead.

This month’s numbers represent an improvement for Udall from July, when he led by just four percentage points. But he has yet to regain the nine-point lead he had over Schaffer in June.

Udall and Schaffer are competing for the right to replace retiring Republican Senator Wayne Allard. A Udall win could mean more bad news for the Republicans in the Senate, who are at risk of losing even more seats to the Democrats this fall. Other Republican seats at risk include Alaska, New Hampshire, New Mexico, Colorado, Mississippi, Kansas, Virginia and Kentucky.

Though both candidates receive equal support from members of their own parties, Udall has a 48% to 30% lead among unaffiliated voters. Last month, his lead was three points higher among those voters. Udall leads 53% to 32% among women in Colorado but trails Schaffer 51% to 39% among men.

The Democrat is viewed favorably by 53% and unfavorably by 39%. The GOP candidate’s ratings are 48% favorable, 38% unfavorable.

Rasmussen Markets data suggests that Udall has a 76.9% chance of winning Colorado’s Senate race in November. These results are updated on a 24/7 basis by market participants. It costs nothing to join and add your voice to the collective wisdom.

Colorado's Democratic Governor Bill Ritter earns good or excellent ratings from 49%, up from 41% last month. A quarter (24%) says he is doing a poor job.

The presidential election in Colorado this month is a toss-up.