A Quinnipiac University poll released Thursday showed a virtually tied race for Senate in Colorado.  

Democratic Sen. Mark Udall led his GOP challenger, Rep. Cory Gardner, by a single point  — 45 percent to 44 percent — in the survey. That split was within the poll’s margin of error of 2.7 points.  

This survey was the first independent, live-interview poll conducted in the race since Gardner announced his candidacy in March. Until then, Udall had not attracted any top-tier opposition, but Gardner’s entrance into the race immediately made the contest more competitive.  

Eight percent of registered Colorado voters polled said they were undecided.  

The survey also found a big gender gap, with 52 percent of female voters saying they would vote for Udall if the election were today, compared to 35 percent who said they would vote for Gardner.  

Udall’s campaign has been working to exploit that gender gap: His first campaign ad, released earlier this week, attacks Gardner on abortion and birth control, suggesting the Republican does not “respect” women.  

A plurality, 46 percent, of survey respondents said Udall does not deserve to be re-elected, while 40 percent said he does. About 43 percent of survey respondents viewed Udall favorably, while 38 percent viewed him unfavorably.  

Half of the voters polled said they were still unfamiliar with Gardner, a second-term congressman who has never run for statewide office. Among those who know him, 30 percent had a favorable view of him and 18 percent had an unfavorable view.  

Quinnipiac University surveyed 1,298 registered voters in Colorado from April 15-21 using live interviewers, calling both land lines and cellphones.  

The results are similar to an internal poll conducted  for the U.S. Chamber of Commerce. That survey found Gardner narrowly ahead of Udall, 44 percent to 42 percent, with a margin of error of 4 points.  

The Colorado race is rated Lean Democrat by the Rothenberg Political Report/Roll Call.