PORTSMOUTH, Ohio (AP) ― Republican presidential nominee Mitt Romney and his running mate Paul Ryan focused on rallying supporters Saturday in the pivotal state of Ohio, hammering at President Barack Obama for going easy on China over unfair trade practices. Obama took precious time off the campaign trail to practice for the next critical debate against his Republican rival.

Both sides are devoting huge time and effort to Ohio, this year’s battleground to end all battlegrounds, where polls show Obama with a slight edge over Romney. The campaigns are furiously organizing ground troops to lock in ballots in states like Ohio where early voting is already under way.

Ohio is crucial for Romney because his path to winning the 270 Electoral College votes he needs to win the election is far narrower if he can’t win Ohio. Losing here would mean he’d have to win almost all of the other up-for-grabs battleground states. No Republican candidate has won the presidency without taking Ohio.

The U.S. president is not chosen by a nationwide popular vote but in state-by-state contests, making swing states like Ohio ― which are neither reliably Republican nor Democratic ― important in such a tight election

Both campaigns also are keenly aware of the importance of this year’s series of three presidential debates. Romney’s strong performance in the first debate on Oct. 3 gave his campaign a much-needed jolt of energy. Joe Biden’s aggressive counterpunch in a debate with Republican vice presidential candidate Paul Ryan on Thursday cheered Democrats, but some critics thought the vice president overdid the theatrics with his frequent eye rolls, headshakes and broad grins suggesting incredulity.

Obama’s upcoming schedule is an unspoken acknowledgment of the importance that the president attaches to upping his game in the upcoming debate. The president is largely dropping out of sight for five straight days in the final weeks of the race to prepare for Tuesday’s encounter in Hempstead, New York.

Campaign officials sought to keep details of Obama’s preparations secret. But they said the president was working on being more aggressive in responding to Romney and calling the Republican out on issues as well as pointing out what they maintain are Romney’s true positions.

Even while cloistered for debate preparation at a resort in Williamsburg, Virginia, though, the president didn’t completely cede the spotlight to Romney. His weekly radio and Internet address highlighted the Obama administration’s work to revive the U.S. auto industry ― a message aimed squarely at working-class voters in manufacturing-heavy states like Ohio.

Romney opposed using government funds to help the auto industry go through bankruptcy. Many analysts believe the industry would not have survived if it had relied on private investment for rescue. It’s an issue that has dogged Romney in Ohio, where numerous auto parts suppliers also benefited from the survival of the big three automakers.

Obama’s campaign upped its celebrity quotient as the two sides claw for any advantage in a tight race: Actor Morgan Freeman’s commanding voice narrates a new feel-good ad telling voters that Obama has met the nation’s challenges and “the last thing we should do is turn back now.”

On Thursday, Bruce Springsteen will team up with former President Bill Clinton to rally Obama voters in Parma, Ohio, in what will be the singer’s first political appearance this campaign. “The Boss’’ also plans a second event Thursday, in Ames, Iowa. Springsteen also campaigned for Obama in 2008.

Romney has spent four of the last five days campaigning in Ohio, trying to connect with working-class voters.

The former Massachusetts governor told a crowd of more than 3,000 at Shawnee State University in Portsmouth on Saturday that Obama was ducking an important decision on whether China is manipulating its currency to gain a trade advantage. A decision was due on Monday, but the Treasury Department said Friday the decision won’t come until after global finance officials meet in early November. That means a decision is unlikely before the Nov. 6 election.

“It’s time for us to stand up to China for their cheating,’’ Romney declared. “It’s got to stop.”

Romney framed the issue squarely as a matter of jobs, saying cheap Chinese products were driving American companies out of business.

“We’ve got to get those jobs back and make trade to be fair,’’ Romney declared.

Ryan, too, criticized the administration for failing to hold China accountable for its trade practices. During a morning appearance in northeastern Ohio at Youngstown State University, he told a crowd of about 1,400 that his hometown of Janesville, Wisconsin, was much like theirs ― a “blue-collar, factory town’’ where the struggles of the auto industry hit home hard.

He faulted Obama for failing to address trade problems with China and said the president had led the country toward a higher national debt, steeper taxes and insufficient job growth.

“We can’t keep going down this path,” he said. “We can’t keep accepting this is the new normal.’’

The Wisconsin congressman then headed to campaign before a college football game at Bowling Green State University, in the northwestern part of the state.

The Obama campaign dismissed the Republicans’ tough talk on China as nothing more than talk.

“Mitt Romney will never crack down on China’s cheating _ just look at his record,’’ Obama campaign spokesman Danny Kanner said in a statement. He said Romney had opposed Obama administration efforts to impose tariffs on Chinese-made tires and had invested in companies that shipped American jobs to China.

Romney spent nearly four hours Saturday morning at a Columbus hotel preparing for the next debate, then boarded his campaign bus for Shawnee State. From there, the Romney bus headed for Lebanon in southwest Ohio, where he gave a similar speech to the one he delivered in Portsmouth.

Obama’s campaign has acknowledged he didn’t practice enough before his widely panned performance in the first debate. Some sessions were cut short, others canceled altogether, mainly because of developments in Libya, where four Americans were killed at the U.S. consulate in Benghazi.

The campaign has resisted calls from some Democrats to shake up Obama’s debate team. Senior advisers David Axelrod and David Plouffe, along with former White House officials Anita Dunn and Ron Klain, still are running the preparations, with Sen. John Kerry standing in a Romney.

Tuesday’s town-hall style debate at Hofstra University will have an audience of about 80 undecided voters selected by the Gallup Organization. Moderator Candy Crowley of CNN will select from among questions on foreign and domestic policy submitted by the audience.

The final debate, covering foreign policy, will be Oct. 22 in Boca Raton, Florida.