This article is from the archive of our partner National Journal

For President Obama, the battle with his party over trade promotion authority is the latest sign of his diminishing clout with his party and looming lame duck status. But for Senate Democrats looking to take back the majority in 2016, the intraparty divide is creating a golden opportunity for their recruits to showcase their populist bona fides while also breaking from an unpopular president on a signature issue.

The issue of trade is a unique issue for Democrats that's a political twofer: It allows Democrats to hit Republicans for being too close to moneyed interests—a line of attack that worked against Mitt Romney in 2012—while aggressively demonstrating their independence from Obama. It gives them a chance to stop the bleeding with working-class white voters, who have abandoned the Democratic Party in recent years. It was no coincidence that Hillary Clinton, a champion of past free trade deals, sounded awfully lukewarm about the administration's proposed Pacific trade pact.

Democratic officials already are planning to make trade a central issue in Ohio during the Senate race between Sen. Rob Portman and former Gov. Ted Strickland. Party leaders have polling data showing that trade and outsourcing are deeply resonant issues for voters in the state, and the most potent line of attack against the Bush administration's former trade representative. And in other Rust Belt battlegrounds across the Midwest, from Pennsylvania to Missouri, Democrats are hoping that the issue will linger into the presidential campaign year.

And in a sign that the issue has resonance beyond the blue-collar bedrocks, Rep. Patrick Murphy of Florida came out against giving the president "fast-track authority" despite being one of the Chamber of Commerce's most supportive Democrats in the House. Murphy is running for the Senate and faces a possible challenge from his left in Rep. Alan Grayson. Even though Florida has a smaller manufacturing base than in the Midwestern battlegrounds, Murphy's ability to inoculate himself from liberal criticism and maintain a position against the president was too good of a political opportunity to pass up.

"Politically, I'm not sure there is much of an upside to sticking with the President on this. Progressives are largely against this and moderate to independent voters do not have well-formed opinions," said veteran Democratic strategist John Rowley. "In the past, trade bills were political time bombs that became politically problematic years later in primaries and general elections."

Ohio is emerging as the leading bellwether over the political potency of trade. Portman, benefiting from running during a Republican wave in 2010, didn't have to worry as much about attacks over his support for free trade in his first statewide campaign. With more than a year before the election, Strickland already has come out aggressively against Portman for "outsourcing Ohio jobs" and declaring how trade will be a defining issue in the campaign. In a sign that Portman understands the need to bolster his populist profile, he's been pushing an amendment cracking down on currency manipulation for the fast-track trade legislation.

Even as Portman is well-respected inside the Beltway, he has a more difficult task in selling his record to Ohio voters. A Quinnipiac poll last month showed a 44 percent plurality of Ohio voters unfamiliar with him after being asked if they view him favorably. Strickland, benefiting from high recognition as the state's former governor, led Portman by nine points in a head-to-head matchup. To reach out to working-class voters unfamiliar with Portman's record, Strickland is planning to define Portman early on as someone more focused on Wall Street than Main Street.

"People talk about the fact that this is going to be a political issue," Portman said. "People don't want to play politics with it. What they want is a balanced approach. We want more exports, and we also want a more level playing field. He's trying to change the topic because he's been a terrible governor in terms of jobs. Ohio lost 350,000 jobs under his watch; he's hardly in a position to lecture any of us about jobs."

As significant is whether trade will remain resonant in other Rust Belt Senate battlegrounds, where populism has often been wielded as a powerful political weapon. In these races, Democrats have the benefit of running against first-term senators whose profiles cut closer towards the white-collar segment of the electorate.

In Pennsylvania, Sen. Pat Toomey headed the pro-trade, fiscally-conservative Club for Growth before being elected to the Senate, a biographical point that his Democratic challengers are expected to exploit again in 2016. Toomey voted for fast-track trade authority in the Senate Finance Committee, putting him at odds with his in-state colleague, Sen. Robert Casey. Adding to the issue's potency: The state has lost 43,000 manufacturing jobs since Obama has been in office, one of the steepest declines of any state, according to the Bureau of Labor Statistics.

In Wisconsin, Sen. Ron Johnson parlayed his career as a successful businessman to the Senate in 2010, but Democrats will be aggressively hitting him over his voting record six years later. Johnson is an outspoken advocate of free trade, even acknowledging to The Washington Post that it's "not the most politically popular thing to be for" in his home state. Johnson likely is facing a rematch against Democratic former Sen. Russ Feingold, whom he defeated in 2010.

Democrats also are hoping to use the issue of trade policy against two other freshmen up in 2016: Sen. Mark Kirk of Illinois, who represented one of the most affluent Congressional districts in the House, and Sen. Roy Blunt of Missouri, where Democrats desperately need to make inroads with working-class whites to have a credible shot at ousting the incumbent. They're running Secretary of State Jason Kander, a military veteran who served in Afghanistan, against Blunt in hopes of appealing to that constituency.

Indeed, what makes this trade fight so consequential is that the path for Democrats to regain control of the upper chamber runs through those populist-minded Rust Belt voters that have drifted away from the party in recent years. Democrats performed so poorly in these Midwestern battlegrounds in 2010 that even their well-liked nominees ran behind President Obama in 2012 with those working-class voters. If there's a way to get them back, it's over fiscal issues where Republicans are vulnerable over being too close to corporate interests.

"Free trade and fast track have become flash points for that generalized economic anxiety and insecurity Americans feel," said one Democratic strategist. "Democrats are now feeling more liberated and willing to break with President Obama these days when it's in their political interest."

This article is from the archive of our partner National Journal.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.