“We don't win on trade.”

That message, repeated daily by Republican presidential candidate Donald Trump, has helped him win the support of wide swaths of the white working class. For many top Republican campaign donors, however, that message runs contrary to free trade stance the party has held for generations.

And yet Trump's opposition to trade policies sacrosanct to corporate America have not spurred moneyed business elites to back political groups opposing the current GOP front-runner. Instead, corporate political donors have tightened their purse strings in apparent anticipation of the dust settling on a tumultuous political season.

“On the corporate side, we’ve seen a lot of fence-sitting,” Jennifer Victor, associate professor of political science at George Mason University, said. “The corporate PACs that tend to get involved simply haven’t yet.”

In part, that’s because corporate campaign finance vehicles like political action committees, or PACs, tend to keep their spending muted until the primaries are over and the general election opponents have emerged. That’s when corporate interests utilize most the liberties granted by the 2010 Citizens United Supreme Court decision, which opened the floodgates of independent political expenditures.

But Trump’s chaotic presence in the Republican primary has upended the 2012 playbook. “His candidacy defies every theory and model and prediction and past history we have about understanding how nominees get chosen,” Victor said.

Corporate interests reliant on trade have cause for concern. Trump has built his economic platform around the idea that, following negotiated trade deals allegedly poorly negotiated, countries like China and Mexico have “killed” the American worker. He has promised to tear up existing trade agreements, while threatening Chinese-made goods with 45 percent tariffs.

“What they've done to us is the greatest single theft in the history of the world,” Trump said of China.

Large corporations and industry groups have a different view. Sales to foreign markets made up a third of total revenue at companies in the Standard & Poor’s 500. And virtually every company that sells consumer goods, from electronics manufacturers to food retailers, relies on intricate global supply chains.

“Global supply chain leaders are concerned about the potential of Trump interfering with free trade,” Kevin O’Marah, chief content officer of supply chain consultant SCM World, said. “The idea that somehow global trade goes from being reasonably free to being impacted by a global trade war is very scary.”

Meg Whitman, Hewlett Packard CEO and former backer of failed GOP contender Chris Christie, has been among the only major corporate leaders to sound alarms on Trump. His trade stance “would sink this country into a recession,” Whitman recently warned on CNBC. “It would penalize global companies that are trying to be competitive.”

Her worries are echoed by Jon Gold of the National Retail Federation (NRF). Gold warned that a Trump presidency — and a trade war with China — could imperil the 7 million retail jobs directly or indirectly tied to global trade. “The U.S. survives and thrives on trade,” Gold said.

For industry groups, however, Trump presents a dilemma. His anti-trade sentiments run against the grain of laissez-faire trade politics typical for Republicans. But opposing him would mean entering a primary scrum that has seen hundreds of millions of dollars in campaign spending blown in vain efforts to outmaneuver the reality TV star.

“We tend to stay out of backing any one candidate on either side,” Gold said. “Once the nominees are named, we’ll have conversations.”

But it’s hard to imagine a conversation with Trump moving very far on the NRF’s support for the Trans Pacific Partnership, for instance, an as-yet unsigned trade pact that Trump has called “a horrible deal.” Potentially covering 40 percent of the world economy, the accord has become a top goal for President Barack Obama in his final year in office.

Support for the TPP has also topped the policy priority list at heavy hitting industry organizations including the Chamber of Commerce and the Business Roundtable. In a survey conducted by the latter group, a majority of American CEOs reported that the TPP would help companies grow and be more competitive.

But John Engler, president of the Business Roundtable, has mostly avoided overtly criticizing Trump in recent months. “It’s not unusual to have people running against trade as candidates,” Engler said last week, suggesting that candidates currently hostile to trade could change their tune once in office. “I think economic reality sets in the moment you’re elected,” Engler told CNBC.

The Chamber of Commerce also refrained from directly addressing Trump. In a statement to International Business Times, the Chamber wrote, “Our message to all the candidates in both parties is the same. We need more trade and more market-opening trade deals — not fewer.”

These groups’ reticence to engage overtly with Trump over trade comes as blue-collar, mostly white workers in regions that have been hard-hit by trade policies stream to Trump’s side. According to research by a senior fellow at the Peterson Institute for International Economics, J. Bradford Jensen, and others, dissatisfied voters in these areas are more likely to back challengers to incumbent parties during presidential elections.

Meanwhile, Jensen said, the chief benefits of trade — like cheaper consumer goods — barely move these voters. Those effects “are not as visceral as when a plant closes,” Jensen said. “If you think you lost your job because of trade, you are going to vote on that.”

On the other side of the coin, just a smattering of business leaders have contributed to efforts to hobble Trump’s seemingly unstoppable campaign to win the GOP nomination.

They include the likes of hedge fund billionaire Paul Singer, who backed Florida Senator Marco Rubio until he dropped out of the race. Singer gave $1 million to Our Principles PAC, which was established to run ads challenging Trump and has also attracted millions of dollars from the family of Joe Ricketts, co-founder of TD Ameritrade.

Our Principles shares donors with Club for Growth, which has also come out against Trump. The family of Arkansas investment banker Warren Stephens has piled a combined $3.5 million into the two political groups.

But the large donors disclosed in campaign filings for these groups have no particular connection to trade; many come from the world of finance. And executives from large, publicly traded companies — who have been found to make political donations at much higher rates than average Americans — are largely absent from the anti-Trump contingent.

They could be anxious not to fight a losing battle. Some donors, witnessing the ease with which Trump has batted down ill-fated attempts by Rubio and also-ran Jeb Bush to slow Trump’s momentum, have moved toward supporting Senate races, the Center for Public Integrity reported.

There’s also good reason to wait. Victor, the political scientist, argued that campaign spending functions more as a way of gaining access to eventual winners than picking who those winners will be. For those simply seeking a seat at the table, it’s no use to try to enter the GOP fray. “Those who want to back the right horse are sitting on the sidelines,” Victor said.

When these donors finally do choose to spend, Victor predicted that Democrat Hillary Clinton, should she defeat left-wing challenger Bernie Sanders, could be the beneficiary if corporate leaders have to pick between her or Trump.

“Trump is going to draw his support from the working class,” Victor said. “In order to offset whatever losses the Democrats might have from that blue-collar crowd, they need to make up that loss someplace. The business interests are the obvious place.”