Hillary Clinton and Bernie Sanders are railing against the Trans-Pacific Partnership in the Democratic primary. On the right, GOP presidential front-runner Donald Trump is ripping the trade deal as a “disaster” negotiated by “incompetent people.”

President Barack Obama’s herculean task of shepherding the landmark Trans-Pacific Partnership through Capitol Hill is about to run into one major hurdle: 2016 presidential politics.

The Obama administration already won one hard-fought battle when trade promotion authority passed in June over opposition from most Democrats. But the booming anti-trade rhetoric animating the Republican and Democratic presidential primaries could complicate the path for Congress to formally approve the trade agreement between the United States and 11 Asia-Pacific nations, officially made public last week.

Obama has little room for error. Pro-trade backers won the June fight by the narrowest of margins in both the House and Senate. The trade pact is the biggest item on Obama’s economic agenda during his last two years in office.

“We only got 13 Democrats in the Senate on TPA,” Senate Majority Whip John Cornyn (R-Texas) said. “There is a concern that with Hillary Clinton and Bernie Sanders on the Democratic side so fervently anti-trade, that I’m not sure whether those Democrat votes will be there.”

When asked whether Clinton’s opposition made it more difficult for pro-trade Democrats to back the sweeping Pacific Rim trade agreement, one Senate Democrat who voted against TPA said bluntly: “Yes.”

On the other end, conservative opponents of Obama’s trade agenda are seizing on Trump’s rise in the Republican presidential primary to blunt momentum for the TPP. The issue has driven a rift through the GOP field: Trump and Ted Cruz are skeptics, while Jeb Bush and Marco Rubio have been warm to it.

“I think Trump’s strength in the Republican primary is in significant part due to his challenging of trade and the fact that he says we haven’t defended American interests effectively,” said Sen. Jeff Sessions (R-Ala.), whose conservative views on trade and immigration align with those of the billionaire mogul.

Congress is far away from a vote on approving or rejecting the sweeping Pacific Rim trade deal among the dozen countries that represent roughly 40 percent of the world’s gross domestic product.

After notifying Congress last Thursday that he intends to sign the TPP, Obama has to wait at least 90 days to actually do so. And then Obama would have to officially submit the deal to Capitol Hill, which would have 90 legislative days to vote on the agreement. The White House and congressional leaders are expected to work in tandem to figure out when Obama would submit the deal to Congress.

There is already speculation that a vote on TPP won’t happen until after the November 2016 elections, which opponents of the trade deal point to as a sign that the issue is getting too hot to tackle before lawmakers up for reelection go before voters.

“I think that evidence is a belief in Congress that the American people don’t want it and that they would prefer to bring it up after an election in a lame duck, perhaps when they might have a better chance of passing it,” Sessions said.

Whenever the TPP fight comes to Congress, it’s sure to echo the ugly and arduous fight that marked the battle to grant Obama trade promotion authority, which is fast-track power that allows the president to submit the trade deal for straight up-or-down votes without any amendments.

In June, just 28 Democrats in the House and 13 Democrats in the Senate backed TPA, which passed the House with 218 votes and the Senate with 60. Under the fast-track law, approval of TPP needs just a simple majority as long as lawmakers believe the trade deal meets the requirements laid out under trade promotion authority.

Republicans, who control both chambers of Congress, are expected to provide most of the votes for Obama’s trade deal, although administration officials are hoping to attract more Democratic support because of labor and environmental standards in the pact that they’re calling robust.

Still, anti-TPP Democrats have a major weapon in their arsenal in Clinton. The likely Democratic standard-bearer came out in opposition to the TPP in October, after calling it the “gold standard” of trade agreements as Obama’s secretary of state in 2012.

“Secretary Clinton’s leadership on this issue is a substantial boost to those of us who oppose the TPP,” said Sen. Bob Casey (D-Pa.). “Secretary Clinton’s important statement highlighted an issue that many of us who have serious concerns about the TPP have been focused on — the issue of currency manipulation.”

There’s no indication yet from the small cadre of pro-trade Democrats that their support for Obama’s trade agenda is wavering in light of Clinton’s opposition. Those Democrats, who came under fire from the left for their votes in June, could invite even more scrutiny if they decided to flip their trade stance.

Sen. Tom Carper (D-Del.), who voted for trade promotion authority, dismissed any influence that the trade opposition from Clinton and Sanders — who bemoaned last week that the TPP is “worse than I thought” — will have on him or other pro-trade Democrats.

“I think at one point she was for it when it was being negotiated,” Carper said of Clinton. “If it actually reads and appears as we’ve been told by the trade ambassador and his staff, I think pro-trade Dems will stick … regardless of Secretary Clinton’s position.”

In addition to Carper, Senate Democrats who backed TPA in June are Michael Bennet of Colorado, Maria Cantwell and Patty Murray of Washington, Chris Coons of Delaware, Dianne Feinstein of California, Heidi Heitkamp of North Dakota, Tim Kaine and Mark Warner of Virginia, Claire McCaskill of Missouri, Bill Nelson of Florida, Jeanne Shaheen of New Hampshire and Ron Wyden of Oregon. Bennet could face a competitive reelection bid next year.

In the Senate, 2016 politics aren’t the only obstacle that TPP backers will have to navigate.

Cornyn said the administration’s decision not to lift the ban on crude oil exports in conjunction with the trade agreement “certainly dims my enthusiasm.” Sen. Thom Tillis (R-N.C.) said he’s “absolutely against” TPP as written because of intellectual property provisions for biologics — a new class of drugs made from living cells — and pharmaceuticals, as well as the omission of tobacco from the TPP’s investor protections. Fellow North Carolina Republican Sen. Richard Burr has similar concerns.

All three Senate Republicans backed trade promotion authority in June.

“I think it has serious problems with being passed next year,” Tillis said.

Even Senate Finance Committee Chairman Orrin Hatch (R-Utah), one of the staunchest proponents of trade authority, has major concerns with the negotiated agreement as it’s been described. He told the U.S. Chamber of Commerce last Friday that the current draft of TPP “falls short” and that U.S. trade officials may have to renegotiate the deal.

Pro-trade lawmakers are urging colleagues to reserve judgment until they’ve had a chance to fully review the text of the agreement. And they’re touting the transparency of the TPP, arguing that’s what really matters, not presidential politics.

“Both sides over the years got up and said, ‘You know what’s really bad about trade is, it’s all these sleazy deals being done in the dead of backrooms and nobody knows what’s going on,’” said Wyden, the top Democrat on the Finance Committee. “Now, before … any senator or congressperson casts a vote in the Senate and in the House, there will be months of sunshine for people to really get into the issue. That’s what’s new here.”