In the first debate of their heated U.S. Senate race, the incumbent Democrat’s attacks last night on the policy positions of his Republican challenger took on a personal tone.

Rep. Tom Cotton, the challenger, and Sen. Mark Pryor, the incumbent, squared off at the University of Central Arkansas in Conway. Joining them to debate who would serve Arkansas best in the Senate: Libertarian candidate Nathan LaFrance and Green Party candidate Mark Swaney.

Pryor and Cotton touched on familiar themes such as Obamacare, the farm bill and the growing threat from the ISIS terrorist group, but used the debate to take personal shots at one another.

As he has throughout the campaign, Pryor repeatedly hammered Cotton for pursuing a Senate bid while still in his first term in the House of Representatives.

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“He didn’t even know where the bathrooms were,” Pryor said after criticizing Cotton for conducting a poll early in his tenure to determine how likely a win against Pryor would be.

The Democratic incumbent warned Arkansans that Cotton would do little to reach across the aisle and work with Democrats.

“Congressman, you don’t have the reputation, the ability or the desire to walk across the aisle to get things done in Washington,” Pryor said.

His Republican challenger, though, cited his military service as helping him prepare for the Senate.

“I learned leadership in the streets of Baghdad and the mountains of Afghanistan,” Cotton said. “And let me tell you, you can learn a little more there than you can in the halls of Congress. Leadership requires toughness. It requires courage. Senator Pryor simply isn’t tough enough to stand up to Barack Obama and put Arkansas first.”

After graduating from Harvard Law School, Cotton joined the Army. He completed two tours in Iraq and Afghanistan and was honorably discharged as a captain.

Cotton repeatedly tied Pryor to President Obama — a move being used by Republicans in tight races because the president faces low approval ratings nationwide.

In the 2012 election, Obama won 36.9 percent of the vote in Arkansas. In 2008 he did only slightly better, garnering 38.8 percent.

“Obama has said his policies are on the ballot, every single one of them, and I agree,” Cotton said. “In Arkansas, those policies are called Mark Pryor.”

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Pryor, though, offered a rebuttal.

“Clearly, Congressman Cotton is running against one man,” he said. “But I’m running for 3 million Arkansans.”

The incumbent Democrat has focused on criticizing Cotton for a lack of experience in Congress. During an interview with MSNBC in March, Pryor said Cotton had an air of “entitlement.”

“I think that’s part of that sense of entitlement that he gives off is that, almost like, ‘I served my country, let me into the Senate,’ ” Pryor said.

Cotton countered Pryor’s comment with an ad featuring his old drill instructor and highlighting qualities instilled in him during basic training: accountability, humility and “putting the unit before yourself.”

Tonight, Cotton and Pryor are slated to go head-to-head in their second debate.