"On issues important to the people of Ohio, President Obama has utterly failed to deliver," she said in a statement.
Obama had pledged in 2008 to take steps against China over allegedly improper currency manipulation. Critics charge that Beijing keeps its currency, the yuan, artificially low against the dollar, giving its exports an unfair advantage over Americans goods.
Even in the scorching heat, Obama's supporters chanted that they were "fired up, ready to go."
Sharon Belkofer, 69, told Yahoo News that she forged a connection with Obama when she met him at Fort Drum, after her son was killed in Afghanistan.
"The president was so kind an compassionate. He hugged me, let me cry all over his suit," she said. "We need him. We need him for another four years."
Belkofer, who calls nearby Perrysburg home, said she knew Obama was in for a fight. "We're not foolish enough to think that, just because we think he's fabulous, everyone is going to vote for him."
"We need to work for him. We need to fight for him," she said.
Jeff MacKenzie, who teaches high school science and lives in nearby Toledo, told Yahoo News he was "hoping the president gets another four years." Why? "Because this country was a mess when he took it over, and he's really started to turn things around."
"Obamacare, in particular, is one of his greatest achievements. This country's too great to have people who don't have health insurance," said MacKenzie, 53.
MacKenzie has been touched by the law: His 24-year-old daughter recently lost her job as a special education teacher—and with it, her insurance. "So she's on my plan now," he said. "You know things are bad when special ed teachers are losing their jobs."