Sen. Rob Portman of Ohio is maneuvering with care as he runs for re-election in a swing state while cautiously supporting a free-trade deal that even some fellow Republicans fear could lead to job losses back home.

The former U.S. trade representative backed the fast-track trade bill in a Senate committee. But that was only after pushing an amendment aimed at cracking down on currency manipulation, a measure the Obama administration saw as a deal killer for the bill.

Portman's oft-repeated explanation: "I'm for a balanced approach on trade."

But Democrats are pouncing, convinced they've found an issue that could deny Portman a second term as they battle uphill to retake control of the Senate.

"I'm for protecting Ohio jobs and Ohio companies and he's for outsourcing Ohio jobs," said former Ohio Gov. Ted Strickland, Portman's likely Democratic opponent next year. "This is going to be a huge issue and maybe the most defining issue between the two of us."

Adding to Portman's predicament: his service for a year prior to joining the Senate as President George W. Bush's trade representative, the executive branch official charged with negotiating trade deals with other countries.

His name was conspicuously missing from a letter that every other trade representative in the last three decades sent to congressional leaders earlier this month. The former trade officials were pushing for approval of the fast-track trade bill, which would pave the way for a landmark deal with Asian nations by allowing President Barack Obama to negotiate trade pacts that Congress must accept or reject without amending.

Portman's amendment, aimed at blocking foreign nations from manipulating their currencies to the detriment of American products, failed in the Senate Finance Committee as critics warned it could scare off other nations from signing onto trade deals with the U.S.

Portman said he will continue pushing for the measure when the fast-track bill comes to the Senate floor later this month. For now he's declining to say definitively whether he will vote for the bill on final consideration, saying he supports the aims of the legislation but wants to see the final product as amended before declaring his position.

"America needs to be tougher on enforcement, tougher on leveling the playing field, but we can't give up these overseas markets where 90 percent of consumers live, because we want better-paying jobs in Ohio and more jobs. That is obviously key to our state," he said. "If you care about Ohio workers and farmers, you should be for more exports and if you're not, you should have to explain that."

Portman's move on the currency amendment earned him a scathing editorial in The Wall Street Journal -- but an approving one from the home-state Toledo Blade. That divide illustrates the cross-currents Portman must navigate as he faces pressure from traditional Republican business constituencies to support the trade deal, while assuring Ohio voters that he's looking out for their interests.

Many of those voters feel betrayed by past deals, particularly the North American Free Trade Agreement, blaming them for job and manufacturing losses that shuttered factories across the state and ravaged the economy. The economy has regained strength and some jobs have come back, but labor unions and some working-class voters still look with deep distrust on trade deals, even as debate rages about their precise role in the state's manufacturing decline.

"It's an issue obviously that divides voters and divides politicians. Labor unions in particular are vociferous," said Paul A. Beck, a professor emeritus of political science at Ohio State University. "It carries a lot of symbolic weight."

Ohio Democrats have been pounding Portman relentlessly on the issue well over a year before he will face voters in his politically divided state. Although the soft-spoken and hard-working Portman, 59, is seen as a solid incumbent who will be tough to beat, Democratic turnout tends to increase in presidential election years. Ohio is a top target as Democrats aim to pick up the net five seats they would need to retake Senate control (four if they hang onto the White House and can send a Democratic vice president to cast tie-breaking votes).

But divisions over trade go beyond Republicans versus Democrats. Even some Ohio Republicans, particularly from areas of the state that once hosted manufacturing jobs that have not come back, are opposing the fast-track bill.

"People connote the idea of trade bills with hurting the economy. They don't see a benefit to that," said GOP Rep. Dave Joyce, whose northeast Ohio district includes industrial regions. "And so if there is and I'm wrong, God bless. I hope it does do things to stimulate economy and certainly that'll fare better for Sen. Portman."

Even the state's GOP governor, John Kasich, is refusing to take a position on the bill, telling reporters at a lunch hosted by The Christian Science Monitor on Friday that he would have to see the final deal before weighing in.

For his part, Portman continues a balancing act that has him boasting of working with his state's liberal Democratic senator, Sherrod Brown, a vocal opponent of the fast-track bill, and against his own party's leaders.

"We're out there fighting the good fight," Portman said.