President Barack Obama finds himself in unfamiliar — and uncomfortable — territory. In working out a Pacific trade deal, the president is surrounded in general agreement by Republicans even as the Democratic base — among whom he’s more accustomed to being held up in near deistic adulation — is staring at him from across the room, teeth bared, indignant he would commit such heresy as pursuing a free trade agreement.

Trade policy is a complicated business. Consider first the raw economic analysis. Economists are virtually unanimous (as odd as that might be) in their agreement free trade is a good thing, that the man who’s talented and adept at building furniture is far better off buying clothes from the man who’s talented and adept at making clothing than he is by attempting to make his own.

This is called comparative advantage, and it has become a staple of economic thinking. Even liberal economists, by and large, are at a loss to resist this particular truth. Like the furniture builder, nations profit when they concentrate their efforts on those activities more in line with their national skills and they can do better than others. This has largely put the old “outsourcing” argument to rest. Yes, America has lost some textile and weaving jobs to certain other countries. But it’s because they’ve been replaced by better-paying high-tech pursuits.

This is the reality with which Obama is confronted. But he faces increasing opposition from the left wing of his party, for whom free trade is seen as a euphemism for bulldozing workers’ rights and auctioning off of American jobs.

Trade might have solid empirical backing, but there are other considerations, extrinsic to economic analysis, that weigh heavily on the policy maker. How, for instance, do you convince American sugar beet growers they should back a policy that eliminates the U.S. sugar tariff? Perhaps you can’t. But sooner or later, the force of the economic argument tends to win the day.

So President Obama, mugged by an economic reality even his flexible imagination can’t conquer, is forced to cozy up with the GOP to pass a trade bill and concomitant “fast track” authority, whatever Chuck Schumer, Elizabeth Warren and Bernie Sanders have to say about it.

As a bonus, it gives Hillary Clinton one more reason to hate her former boss.

Naturally, there’s an election-year element to all of this. If Obama is in a tough position over the trade pact, it’s several times trickier for Clinton. Remember NAFTA? When her husband was working out the details of that one, she was positively Adam Smith when it came to free trade.

But lo, now she’s faced with the prospect of alienating large and powerful voting blocs she’s depending upon to carry her through the primaries and into the White House. The environmentalists, unions and grassroots activists are all ferociously opposed to this (or any) trade deal.

This is something of a dilemma for Hillary. Political pressure from the AFL-CIO is a problem that won’t go away simply by wiping a server. Her response has been to equivocate. How about this answer to an inquiry in New Hampshire on the matter: “Any trade deal has to produce jobs and raise wages and increase prosperity and protect our security.” That is on the order of saying “any dish must be tasty, filling and provide basic nutritional support” when asked to choose between beef or chicken for dinner.

How much this will ultimately mean politically remains an open question. She remains, of course, the Democratic front-runner by a long shot. It’s difficult to imagine the AFL-CIO or Sierra Club abandoning her over this single issue. But it puts to the question her ability to lead and make tough choices, which is the persona she’s been trying to cultivate since before 2008. And she must surely be cognizant of the possibility of an insurrection from the left. A lot of ambitious Democrats are making noise about the issue, including Warren, whose name just keeps coming up. Sanders has indicated a desire to mount an independent run and could just shed enough votes from the far left to pull off a reverse-Perot.

Meanwhile, this could shape into an early GOP opportunity. Free trade is a pretty easy issue for the free market-loving, economically literate Republican set, should any of the candidates be willing to accept the gift.