Obama, Romney clash over economy, health care NEW: Obama and Romney spar over health care, economic plans The candidates say the other's plans won't work The 90-minute debate is first of three for Obama, Romney Jim Lehrer of PBS moderates his 12th presidential debate (CNN) -- President Barack Obama and Republican challenger Mitt Romney described differing tax and economic plans at their first presidential debate on Wednesday night, arguing the other's proposals won't work in a continuation of major themes from their campaigns. In exchanges full of policy proposals, facts and figures, Romney was more aggressive in the 90-minute encounter in criticizing Obama's record and depicting the president's vision as one of big government while Obama firmly defended his record and challenged his rival's prescriptions as unworkable. "America does best when the middle class does best," Obama said in response to a question on job creation, adding that Romney's plan of tax cuts for the rich had failed before and would fail again now. Describing the Romney tax plan as a $5 trillion cut, Obama echoed a line from former President Bill Clinton by saying the math doesn't add up without increasing tax revenue, which Romney rejects. What questions went unanswered? Share your thoughts with CNN iReport. "I think math, common sense and our history shows us that's not a recipe for job growth," Obama said. Romney, however, said Obama still pushed the same policies as when he took office four years earlier, and those steps had failed to bring down high unemployment and get the economy surging again. "It's going to take a different path," Romney said, repeating his five-point plan for growth that has been part of his stump speech He rejected Obama's characterization of his tax plan, saying it won't add to the deficit, and criticized the president's call for allowing tax rates on income over $250,000 for families and $200,000 for individuals to return to the higher rates of the 1990s. The National Federation for Independent Businesses has said that will cost 750,000 jobs. I don't want to cost jobs," Romney said. Obama responded that the revenue issue is "a major difference" he has with Romney, noting the former Massachusetts governor rejected the idea of cutting $10 in spending for every $1 in new revenue during the Republican primary campaign. The candidates later clashed over major reform bills passed in Obama's first term, with Romney repeating his past pledge to repeal and replace the health care reform act and the Wall Street reform bill. Insisting that regulation was necessary to keep the economy functioning, Romney said the Dodd-Frank Act passed in response to the financial crisis of 2008 was in some cases excessive. He also repeated past criticism that the Affordable Care Act passed with no Republican support amounted to an unnecessary and unwanted government takeover of health care. "The right answer is not to have the federal government take over health care," Romney said, adding his plan would include popular provisions of Obamacare such as allowing children up to age 26 stay on family plans and preventing insurers from denying coverage for pre-existing conditions. Obama, however, said Romney has yet to provide full details of proposals to replace the Wall Street and health care reforms he has vowed to repeal. "At some point, the American people have to ask themselves if the reason that Governor Romney is keeping all these plan secret is because they're too good," Obama said. Debates by the numbers Romney has more recent debate experience -- he took part in 22 during the grueling GOP primary campaign of 2011-2012 that he ended up winning handily after fending off a litany of conservative contenders.