"My opponent has been running around Ohio claiming he's going to roll up his sleeves and he's going to take the fight to China," Mr. Obama told a crowd of Ohioans at a rally in Cincinnati. "You can't stand up to China when all you've done is send them our jobs."
On Monday, Obama underscored his message by filing suit with the World Trade Organization against China for unfair trade practices. In the suit – the second one against China that Obama has filed recently – the US charges that China is unfairly subsidizing its cars and auto parts for export.
"Many people [in Ohio] come out of that tradition and context where heavy manufacturing was important and are very sensitive to ... where manufacturing has moved jobs overseas," says Paul Beck, a political scientist at Ohio State University in Columbus.
While Obama talks up his trade policy and actions against Romney, his opponent has fired back, claiming that Obama's criticism of China now is all political, and that he's failed to act to help American manufacturers during his presidency.
"Campaign-season trade cases may sound good on the stump, but it is too little, too late for American businesses and middle-class families," Romney said in a statement. "I will not wait until the last months of my presidency to stand up to China, or do so only when votes are at stake. From day one, I will pursue a comprehensive strategy to confront China's unfair trade practices and ensure a level playing field where our businesses can compete and win."
His campaign also played up the loss of jobs that has occurred during Obama's tenure.
"American manufacturing is struggling in the Obama economy," said Amanda Henneberg, a Romney campaign spokeswoman. "The president's misguided, ineffective policies have hampered the private sector and allowed China to flaunt the rules while middle-class families suffer."
But the issue is a tough one for Republicans, notes Professor Beck, because they're generally viewed as favoring free trade. And it's even tougher for Romney, who carries extra baggage on the issue due to his tenure at Bain Capital. Many voters see his work there as contributing to moving American jobs overseas.
Trade and job loss overseas is "still an issue that plays into the hands of Democrats, with China being the symbol right now," says Beck.
Obama is losing no chance to drive that point home, rebutting Romney's claims that his administration hasn't done enough to curb China's unfair trade practices with his own statements questioning Romney's credibility.
In one new Obama ad now playing in nine swing states, including Ohio, the ad opens with Romney saying, "it is time to stand up to the cheaters and make sure we protect jobs for the American people," before launching into an attack of that message.
"Mitt Romney? Tough on China?" the narrator asks. "Romney's companies were called pioneers in shipping US manufacturing jobs overseas. He invested in firms that specialized in relocating jobs to low-wage countries like China." The ad charges that some of Romney's fortune is invested in China, before concluding, "Romney's never stood up to China. All he's done is to send them our jobs."
Obama, who lost the 2008 Democratic primary in Ohio to Hillary Rodham Clinton by a sizable margin, may have other challenges in Ohio. Some working-class white voters again have been slower to embrace him, as he lacks the union roots that appeal to many Democratic voters in the state.
But his bailout of the auto industry helps Obama with many such voters, says Beck, and gives him some credibility – including with swing voters – that may be tougher for Romney to achieve.
At this point, the state seems to be leaning slightly toward Obama, with polls averaging about a four-point advantage for Obama. Pollster Nate Silver, who keeps a running weighted projection for all states at The New York Times's FiveThirtyEight blog, gives Obama a three-point advantage and a 72 percent chance of winning the state.
Bashing China is low-hanging fruit for both campaigns as they try to attract Ohio voters; the issue will be who comes across as having more credibility.
As he spoke to Ohioans Monday, Obama sought to remind them of actions he has taken – not just the suit he announced today, but in the past.
“We’ve brought more trade cases against China in one term than the previous administration did in two – and every case we’ve brought that’s been decided, we won," he told them. In July, Obama also announced a complaint against China on the eve of a campaign trip to Ohio. In that case, he filed suit over billions of dollars in duties that China levied on American automobiles.
Meanwhile, Romney, in campaign appearances and in his own ads, has highlighted Obama's failure to label China a currency manipulator.
"Seven times, Obama could have stopped China's cheating. Seven times, he refused," says one current Romney ad that takes on the China issue.
"Under Obama," the narrator in the ad says, "we've lost over half a million manufacturing jobs, and for the first time, China is beating us."