Republican Cory Gardner leads incumbent Democrat Mark Udall in the fourth straight poll of the U.S. Senate race in Colorado. The new Quinnipiac poll of likely Colorado voters finds Gardner ahead of Udall by 6 points, 47 percent to 41 percent, while 8 percent support an independent candidate. With that independent discounted and in a head-to-head match-up, Gardner leads 49 percent to 44 percent.