U.S. Sen. Mark Udall, D-Colo., left, takes part in a debate with Republican challenger U.S. Rep. Cory Gardner, R-Colo., at The Denver Post in Denver on Tuesday, Oct. 7, 2014.

(AP Photo/David Zalubowski)

Democratic Sen. Mark Udall and Republican U.S. Rep. Cory Gardner traded blows on Tuesday at a tense debate moderated by the Denver Post.

The hour-long debate was the second of three scheduled for this week, making it an important stretch in a pivotal campaign that could decide the balance of the U.S. Senate.

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Among other issues, the candidates touched on the country’s response to Islamic extremism in the Middle East, the economy in Colorado, and, in keeping with a campaign theme, women’s health.

Personhood and health care

From the get-go, Gardner was put on the defense for his co-sponsorship of a federal “personhood” bill. The legislation, currently stalled in the U.S. House, would define an unborn fetus as a person, and critics charge it would effectively ban abortion and severely limit access to contraception. A similar measure, which Gardner says he no longer supports, is on this year’s ballot in Colorado.

“[The federal] bill is a statement that I support life,” Gardner said.

Gardner has distanced himself from the issue all together, starting in a March interview with the Denver Post and recently in an appearance on Fox 31.

He continued that trend on Tuesday. "It's simply outrageous that somebody would try to ban birth control,” Gardner said, adding that he supports expanded access to over-the-counter birth control.

Udall has hammered Gardner over personhood throughout the campaign, and took many opportunities to return to the issue on Tuesday.

On the Affordable Care Act, Gardner said Udall’s support for Obamacare hurt thousands of Coloradans who saw discontinued plans or increased premiums.

“Senator Udall promised they could keep their health care plan if they liked it. He didn’t say ‘If I liked your plan you can keep it.’ But that’s exactly what happened,” Gardner said.

Udall replied that he was “at the doorstep of the White House” about Coloradans losing their plans. But he noted that the vast majority of people affected also were given alternatives similar to their original plan.

Obamacare "has a lot that was lacking, but we're moving forward in Colorado," Udall said.

Foreign policy

Udall, who sits on the Senate Armed Services Committee, had strong words for Islamic extremists in Iraq and Syria. "We are going to wipe them out," the senator said. "We're going to be there and ask our Arab partners to finally step up."

Gardner said the Obama Administration’s lack of direction has led to the current crisis. He also noted that Udall has missed more than 30 percent of meetings in the Armed Services Committee.

“Where were you?” Gardner asked. Udall replied that he is consistently briefed on the committee’s action and has not missed a vote.

Both candidates said they support comprehensive immigration reform, but neither went into details about measures they’ve supported.

Udall, however, said the U.S. Senate has passed an immigration bill while the House hasn’t.

"I've acted, you haven't," Udall said. In July 2013, he voted for a comprehensive immigration bill that would have secured the U.S.-Mexico border and allowed undocumented students to earn citizenship, among other things. That bill never made it through the House.

Gardner pinned the lack of action on the White House.

“We are in this situation because of failed leadership by the president,” he said.

Jobs and the economy

Udall said Congress should raise the minimum wage to help support low-income Coloradans who’ve been left behind in the ongoing economic recovery. He called it a bipartisan issue.

“The last president to sign a minimum-wage increase was President [George W.] Bush,” he said.

Udall also called for more affordable higher education, and equal pay legislation aimed at closing the gender-based wage gap.

Gardner said his economic plan had four main points: Growing the economy, energy independence, education opportunities and protecting the environment.

“Under Mark Udall and Barack Obama’s failed economy, the jobs aren’t available,” Gardner said.

Gardner later asked Udall why he pays women on his staff less than men, citing allegations first published by a conservative Colorado politics blog.

“I pay the women on my team for equal work,” Udall replied. He said Gardner was trying to distract voters from his own record, which he characterized as a litany of attacks on women’s reproductive rights.

The next debate is scheduled for later this week in Pueblo. Ballots will be mailed out to voters next week.