The tenor of the televised debate in Columbus mirrored the barrage of negative TV ads that have marked a race that is one of the most expensive in the nation.
Mandel, the 35-year-old state treasurer, and Brown, 59, clashed not only personally but on most policy issues — gay marriage, Medicare, trade policy, taxes and government bailouts.
Mandel called the 2008 bailout begun under then-GOP President George Bush "fiscally irresponsible and morally wrong" and said he would not support similar moves if elected.
Mandel at one point urged viewers of the debate to "type in Google Translate" to understand Brown's "Washingtonspeak." He said Brown uses complicated explanations to distract from his poor record, and unemployed Ohioans need someone new.
"Since he went there six years ago? Unemployment, up. Gas prices, up. Health care costs, up. Foreclosure rates, up," Mandel said. "Senator, that's quite a record."
Brown criticized Mandel for failing to support the auto bailout that was connected to 800,000 Ohio jobs and for wanting to privatize Medicare. He said Mandel called his vote for the auto rescue "un-American."
"On the auto rescue, to call that 'Washingtonspeak' is a bit peculiar, because it kept tens of thousands of Ohioans at work," Brown said. "Josh Mandel's view of politics and economics? Tax cuts for the wealthy trickles down. Mine is to focus on the middle class and build the economy out."
Earlier at a presidential campaign event in Wintersville, Democratic former Gov. Ted Strickland said his opposition to the rescue "showed Josh Mandel is not only a bad candidate but a foolish person."
One sharp exchange during the debate was over Brown's vote against Sen. Rand Paul's legislation that would have cut off U.S. aid to Egypt, Pakistan and Libya.
"Sherrod Brown voted to give your money to Libya and Egypt," said Mandel, a two-tour Marine veteran. "Senator, these countries will hate us without you paying them to hate us."
Brown said the bill was overwhelmingly opposed by both Republicans and Democrats, in part because it jeopardized assistance to Israel, the United States' strongest ally in the Middle East.
"That's not Washingtonspeak. That's keeping our country safe," Brown said.
After the debate, U.S. Sen. and 2008 Republican presidential nominee John McCain issued a statement complimenting Mandel's performance.
"Josh proved tonight that he has the experience and knowledge to go toe-to-toe with politicians in Washington responsible for the wasteful spending," McCain said.
Brown said he's won the endorsements of many Ohio newspapers because Mandel has held four offices in seven years and can't be trusted to show up to work. He was referring to the fact that Mandel missed the first 14 monthly meetings of the powerful Board of Deposit that he chairs as treasurer.
"He's more concerned about his next job than the jobs of people in this country," Brown said. "This is hardly somebody who's going to be Mr. Smith Goes to Washington."
After one such exchange, Mandel stared into the camera and said, "Senator, you are a liar," telling viewers Brown has continually directed unjust attacks at his character. He said he would not be bullied by either political party if elected.
Brown replied that calling someone a liar was a new low.
"Being called a liar by the winner of the pants-on-crown-fire is a pretty remarkable thing for a young man to say, or for a man of any age to say in a political debate," Brown said.
He referred to the fact that The Plain Dealer newspaper's truth-squad Politifact column has awarded more of Mandel's statements pants-on-fire rankings for being untrue than any other politician this cycle.
Mandel was a Cleveland-area city councilman and state legislator before being elected state treasurer two years ago. Brown is a former Ohio secretary of state who was elected to the U.S. House in 1992 and is serving his first term in the Senate.
Polls have consistently shown Brown with a slight lead.
The debate was held at the corporate headquarters of Nationwide Insurance in downtown Columbus. It was sponsored by a network of Ohio's eight largest newspapers, The Columbus Dispatch and WBNS-TV.