The growing divide between Mr. Trump and myriad bulwarks of the conservative Republican Party comes as the party races toward its convention in Cleveland next week. The convention is typically the time when the party rallies behind its candidate and develops a set of common policy goals and proposals. “What are they going to do with the Republican platform? I have no idea,” said Stuart Stevens, the chief strategist for Mitt Romney’s 2012 presidential run.
Mr. Trump, with his swaggering, shoot-from-the-hip campaign style, has shown time and again a willingness — nay, an eagerness — to thumb his nose at the hoity-toity members of the Republican establishment, whether big donors like the Koch brothers or powerful entities like the United States Chamber of Commerce.
“They’re a special interest that wants to have the deals that they want to have,” Mr. Trump said to cheers at a packed rally in Bangor, Me., the day after his trade speech. The chamber, he added, was “controlled totally by various groups of people that don’t care about you whatsoever.”
Mr. Trump’s isolationist trade policies play well to individuals who perceive the Republican establishment and their ilk have gotten rich from existing trade policies while their own jobs have moved to lower-wage countries like Mexico or China.
“He’s running as a populist anti-Washington-establishment candidate and there’s hardly a more important organization on the right side of Washington politics than the Chamber of Commerce,” said Richard L. Hall, a professor at the Gerald R. Ford School of Public Policy at the University of Michigan. “But I don’t think the Chamber of Commerce is going to sit silent when Trump is taking positions that run against some of their main themes.”
On its website, the chamber has started to post dire predictions of what a Trump presidency might mean. “Republican front-runner Donald Trump has promised to ‘make America great again,’” began an article posted on the chamber’s website in April. “Does a recession sound ‘great’ to you? Do 7 million lost jobs sound like ‘winning’?”
For much of its existence, the chamber acted as a trade association for American businesses, typically adopting pro-business stances on deregulation of various industries, corporate tax rates and trade agreements.
That changed when Mr. Donohue took over as the chamber president in 1997. The former chief executive of the American Trucking Associations, with his shock of white hair and hard-charging demeanor, Mr. Donohue, 77, morphed the chamber into a political lobbying machine with revenue topping $200 million, according to its 2014 tax filings.
The chamber says it does not get involved in presidential elections, and that is mostly true. The Center for Responsive Politics shows relatively small donations given to Republican presidential candidates over the years.
In 2012, Mr. Romney was the largest recipient, taking in $36,900, according to data compiled by the center.
A spokeswoman for the chamber said any donations to presidential candidates came from individuals in the chamber, rather than the chamber itself. A spokeswoman for the Center for Responsive Politics said its data typically includes donations from company executives because they have the resources to donate and usually do so for business reasons.
While the vast majority of the chamber’s huge cash stockpile goes to its lobbying efforts — $124 million in 2014 — another sizable slice goes to outside advertising. In the midterm elections in 2014, the chamber spent $35 million, overwhelmingly supporting Republican candidates. So far this year, it has spent nearly $14 million, none in support of Democrats.
But to Mr. Trump’s point, the chamber does not publicly describe how it makes decisions regarding what policies or politicians to support. Inside the chamber is a bit murky. Its board is a mix of small-business leaders, trade associations and executives from large corporations, including IBM, Caterpillar, Phillips 66, Dow Chemical Company and Allstate Insurance. But over all, the chamber does not make its membership public.
A search of tax records for donations to the chamber shows that while it has received significant donations from the Bill and Melinda Gates Foundation and the foundation set up by the billionaire investor Steven A. Cohen, some of its biggest contributions have come from the types of conservative political action committees that Mr. Trump likes to target. Crossroads GPS, the PAC founded by Karl Rove, gave $5.2 million to the chamber while Freedom Partners Chamber of Commerce, the PAC founded by the Koch brothers, gave $2 million, according to 2014 tax filings, the most recent that were available.
In an email, a spokeswoman for the chamber responded to a query by noting that the chamber has a “$250 million operation that represents American businesses of all sizes from across the country.”
When not tackling Mr. Trump on trade, the chamber is throwing its considerable political muscle and money behind Republican candidates in critical congressional races who share its ideology on free trade. Those candidates include Senator Rob Portman, who is fighting for re-election in the battleground state of Ohio. Before he entered the Senate, Mr. Portman was the United States trade representative for former President George W. Bush, where he supported the Central American Free Trade Agreement.
Yet Republican strategists are curious how the gap between Mr. Trump and traditional conservatives over trade and other major themes will play out in the coming months.
“Basically, Trump has a position on trade that no one who has ever been a nominee of any party has ever had — a 45 percent tariff on goods,” Mr. Stevens, the Romney strategist, said. “How is that going to work where you have joint efforts between the presidential campaign and the state parties with candidates who want free trade? Are you going to have half the phone bank calling for a 45 percent tariff, and the other half calling for reasonable trade policies?”