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DENVER — With just more than six months before Election Day, Democratic Sen. Mark Udall and his Republican challenger, Rep. Cory Gardner, are in a dead heat, according to a poll by Quinnipiac University that was released Thursday morning.

Udall is favored by 45 percent of voters, while Gardner earned 44 percent, well within the poll’s margin of error of 2.7 percentage points.

“In a race that is both too close to call and one of the prime targets for Republicans trying to take back the Senate, Colorado Sen. Mark Udall might best focus on one predominant concern — the economy,” said Tim Malloy, assistant director of the Quinnipiac University poll.

Sixteen percent of voters listed the economy as the most important issue in the race, with 14 percent saying it’s health care.

“No other issue comes close,” Quinnipiac reported.

Colorado voters are against the Affordable Care Act by 59 percent to 37 percent, according to the poll, something that could hamper Udall, who voted for the measure and has become a target in ads.

There is a huge gender gap, with Udall leading 52 percent to 35 percent among women, while Gardner leads 53 percent to 38 percent among men.

Quinnipiac also asked Colorado voters about their preference on the 2016 presidential race and Sen. Rand Paul, R-Ky., is favored 48 percent to 43 percent for former Secretary of State Hillary Clinton.

“The road to the White House has many twists and turns, but right now, U.S. Sen. Rand Paul is the man to beat in Colorado,” Malloy said.

State voters also disapprove of President Barack Obama’s job performance, 59 percent to 38 percent who approve.

The poll surveyed 1,298 register voters from April 15 to Monday.