Colorado's U.S. Senate race is "too close to call," according to a Quinnipiac University poll released Thursday.
The survey found incumbent U.S. Senate Mark Udall, D-Colo., up 45 to 44 percent over Republican challenger Rep. Cory Gardner.
The race had not been considered close until a few months ago, when the popular Gardner decided to enter. Since then, said a Quinnipiac analysis, the contest has become one of the Republicans' prime targets.
The economy and healthcare "could be the mountains which Democratic incumbent Sen. Mark Udall must climb," the survey reported.
Fifteen percent said the economy or jobs was the most important issue, with 14 percent listing health care.
Those listing health care prefer Gardner, 53 to 40 percent. Among those citing health care, the Republican gets 57 percent support to Udall's 36 percent. Colorado voters oppose the new health care law by a wide margin.