The Republican nominee for an Ohio U.S. Senate seat, state Treasurer Josh Mandel, was booed at the second debate Thursday evening after telling his Democratic opponent, Sen. Sherrod Brown, to "calm down."

The contentious, hour-long debate also featured Mandel calling Brown "a liar." The "calm down" outburst came after Brown exceeded his time limit answering a question on trade practices, prompting a warning from the moderator and an apology from Brown. Mandel pounced.

"Calm down, Senator, calm down," Mandel said, bringing boos from the audience.

Mandel earlier accused Brown of being "a liar" and of telling the "lie of the year" -- a Brown attack on Mandel's record as state treasurer. Brown criticized Mandel's job performance, including reports that he had skipped 14 months of state Board of Deposit meetings, which he chairs, and said Mandel is more interested in running for the next job. Mandel's record as treasurer, including Board of Deposit attendance and his hiring practices, have dominated the Senate race.

"He is hardly someone who will go to Washington and be 'Mr. Smith Goes to Washington,'" Brown said, citing the legendary Frank Capra movie.

Mandel responded, "Senator I take personal offense with that."

Mandel then accused Brown of telling a series of lies on the auto bailout and other issues, similar to a new ad Mandel's campaign and the National Republican Senatorial Committee have released in Ohio. This included Mandel citing press reports that say Brown told lies in campaign ads earlier in the race.

"Senator Brown is a liar," Mandel said.

Brown hit back, citing Mandel's six "Pants on Fire" designations from PolitiFact for false ad claims, the most awarded to any Ohio politician. The designations have been frequent fodder for Brown and Democrats, who gave Mandel a pair of pants for his 35th birthday last month. Mandel returned to the pants to the state Democratic Party.

"Being called a liar by the winner of the pants on fire crown is remarkable," Brown said. ""He goes lower and lower."

Prior to the "liar" exchange, Mandel outlined his qualifications for the Senate seat, highlighting his experience as state treasurer, a state legislator and as a city councilman in Lyndhurst. Mandel also mentioned his experience as a Marine in Iraq and said that prepared him to "stand up" to political bosses as a senator. He said he is prepared to "call out" other senators, lobbyists and the press if elected.

"I have been through tougher stuff than that," Mandel said, citing what has been a familiar theme for military veteran candidates this year, including Missouri secretary of state candidate Jason Kander (D) who made similar statements in a new ad last week.

The debate rehashed several issues that surfaced during the pair's first debate on Monday, including the auto bailout, which Mandel opposes and Brown supports. Mandel continued his attacks on the bailout, saying senators who voted for it should be "ashamed," an attack line he used earlier on Brown.

The two candidates also sparred over same-sex marriage. Brown said he supports it, as well as the repeal of the military's Don't Ask, Don't Tell policy. Mandel said he opposed both, but doesn't condone discrimination.

"I will represent all of the people of Ohio, regardless of their background," Mandel said. "I don't care if you are a Democrat, a Republican, a Libertarian or a vegetarian, I will be blind to race, religion or any kind of orientation."

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