Bolstered by a new poll that shows him leading in Ohio and two other battleground states, President Barack Obama on Wednesday made his ninth campaign trip this year to the Buckeye State to attack Republican rival Mitt Romney's tax plan as unfair to middle-class Americans.

Obama cited a report issued Wednesday by the Urban Institute-Brookings Institution Tax Policy Center that concluded Romney's proposals for tax reform would end up providing large tax cuts to the very wealthy while increasing the tax burden on the lower and middle classes.

"He's asking you to pay more so people like him can get a big tax cut," Obama told more than 2,000 supporters in Mansfield, the first of two Ohio stops Wednesday. "We do not need more tax cuts for folks who are already doing really well."

Romney's campaign challenged the veracity of the study and blamed the president's economic policies for a still-lagging economy.

"President Obama continues to tout liberal studies calling for more tax hikes and more government spending," Romney spokesman Ryan Williams said in a statement. "We've been down that road before -- and it's led us to 41 straight months of unemployment above 8%."

Earlier, the Romney campaign launched a potentially risky ad challenging the Obama administration's auto industry bailout, which is credited with saving General Motors and Chrysler.

With just over three months until the November election, the race has become a contentious struggle to convince voters that the other guy will take the country in the wrong direction.

The Quinnipiac University/CBS News/New York Times poll released Wednesday showed Obama leading Romney in Ohio, Florida and Pennsylvania, all of which are among the eight or so battleground states vital to either candidate's chances for winning.

According to the survey, Obama holds a 50%-44% lead in Ohio and a 51%-45% lead in Florida, which are considered toss-ups in November. The president is ahead 53%-42% in Pennsylvania, which is rated "leans Obama" on the CNN Electoral Map.

"If today were November 6, President Barack Obama would sweep the key swing states of Florida, Ohio and Pennsylvania and -- if history is any guide -- into a second term in the Oval Office," wrote Peter A. Brown, assistant director of the Quinnipiac University Polling Institute, in a statement accompanying the survey's release.

In a key finding that signaled possible trouble for Romney, the candidates were statistically even in all three states on the question of who would better handle the economy.

Romney's main campaign theme is that he is more experienced and better able to bring economic growth than Obama, and his attacks on the president's economic policies have been relentless.

Despite those attacks and unemployment above 8%, Obama is neck-and-neck with the former Massachusetts governor on the issue cited by voters as the most important to them.

Wendy Schiller, a political science professor at Brown University, said before Wednesday's poll came out that the Romney campaign is "betting on economic dissatisfaction" to defeat Obama.

"If that were true, Obama's negatives would be much worse," Schiller said. "There's obviously something else driving people's support other than the economy."

Obama's visit to Ohio showed the importance his campaign places on the state he won in 2008 over Republican candidate Sen. John McCain.

At events in Mansfield and Akron, Obama delivered a modified version of his usual stump speech emphasizing the need to restore the American dream of equal opportunity for all willing to work for it, adding a section on the report by the Tax Policy Center set up by the Urban Institute and the Brookings Institution.

Romney calls for 20% cuts to today's rates as well as eliminating the Alternative Minimum Tax and limiting current deductions, exemptions and credits available to top-level income earners.

However, Romney has yet to say which specific tax breaks he plans to eliminate, and the Tax Policy Center report indicated the result of his plan would force the tax burden to shift toward lower- and middle-class Americans.

Tax policy has become a central economic issue, with Congress deadlocked over proposals to extend most or all of the Bush-era tax cuts set to expire at the end of the year.

Obama calls for extending the current rates under the tax cuts for income below $250,000 for families and $200,000 for individuals, while letting the rates on income above those figures rise to 1990s levels.

"If you're fortunate enough to be in the other 2% of Americans, all we're asking you to do is contribute a little more," Obama said Wednesday. "This includes me, by the way."

Romney and Republicans want to extend all the Bush tax cuts for now to prevent any increase, with both sides calling for comprehensive tax reform after the election as part of necessary deficit reduction steps.

The issue touches on the foundations of the nation's political divide, with Republicans driven by their conservative base seeking to shrink government to reduce deficits while Democrats want a blend of spending cuts and more tax revenue in order to maintain what they consider essential services and entitlement programs.

In its study, the Tax Policy Center did not score Romney's plan directly, saying it lacked sufficient details. Instead, the center said Romney's plan represented a number of Republican proposals.