From the outset, Gary D. Cohn was an unconventional choice to be President Trump’s top economic adviser.
A former Goldman Sachs president and proponent of free trade, Mr. Cohn had a pedigree and economic views that clashed with Mr. Trump’s populist rhetoric and protectionist policies. His methodical approach also contrasted with the president’s freewheeling style.
But Mr. Cohn, who said on Tuesday that he would resign as director of the National Economic Council, brought to the Trump administration something that the president himself lacked: the widespread respect of top corporate executives.
Now, those business leaders are lamenting the loss of one of their own from what is among the country’s most important economic positions.
“Gary brought a strong growth orientation for the economy and a very balanced perspective, particularly on critical topics like trade,” said Rich Lesser, chief executive of the Boston Consulting Group, who served on one of Mr. Trump’s business advisory panels last year and attended policy meetings with Mr. Cohn. “He’ll be missed.”
Mr. Cohn was instrumental in putting together the sweeping tax law that was enacted last year, legislation that delivered a windfall to corporations and was the main policy achievement of Mr. Trump’s first year in office.
He is leaving the White House just as the president is proposing to impose stiff tariffs on imported steel and aluminum, which Mr. Cohn and many of his business allies strongly oppose.
“It’s a pity we’re losing Gary this moment,” said Andrew Liveris, the executive chairman of DowDuPont who was also on a White House advisory panel. “His would have been a critical voice on this issue.”
Markets have been sensitive to Mr. Cohn’s White House arc. In August, amid rumors that he might resign in the wake of Mr. Trump’s equivocal response to white nationalist violence in Charlottesville, Va., stock prices fell before an administration spokesman said that Mr. Cohn planned to stay.
On Tuesday, news of his resignation helped send stock futures down. In early trading on Wednesday, the Standard & Poor’s 500 index slid about 0.5 percent.
“He was extremely reassuring to everyone on Wall Street, and also in the business community,” said Jeffrey A. Sonnenfeld, a professor at the Yale School of Management. “They are losing an oasis of clear thought.”
A former silver trader who sweet-talked his way into his first job at the New York Commodity Exchange and was later the second-highest-ranking executive at Goldman Sachs, Mr. Cohn understood the nuances of free markets and complex organizations, but was not locked into a specific worldview.
As a trader, Mr. Cohn was aggressive in predicting commodity price swings and betting money on his views. As a manager at Goldman, he was tough-minded and could be critical and impatient. His frustration over not being named chief executive was well-telegraphed, not least by his surprise decision to take a job in the Trump administration.
Given his background, he was regarded as the voice of Wall Street in the administration, a mantle that invited admiration and antipathy.
“He is a globalist and he understands economics and trade,” said Bill George, a Goldman board member. “I think he was very stabilizing influence within the Trump administration.”
Kathryn Wylde, the chief executive of the Partnership for New York City, a business group, said that she viewed Mr. Cohn as a “real resource” in Washington.
“He was somebody that the New York business community and financial industry in particular relied on as someone in the White House who understood business and the financial industry and would push for doing what was right, not what was politically correct,” she said.
On Tuesday evening, Lloyd C. Blankfein, Goldman’s chief executive, praised Mr. Cohn in a message on Twitter, writing, “Gary Cohn deserves credit for serving his country in a first class way.”
Mr. Cohn’s role in the administration was not universally celebrated. Some lawmakers, including Senator Elizabeth Warren, Democrat of Massachusetts, were sharply critical of his appointment, saying it was troubling to see a such a critical job go to someone whose firm was deeply connected to the 2008 financial crisis and ensuing recession.
Some of Mr. Trump’s core supporters were also skeptical of Mr. Cohn because of his background. They viewed him as a foe of the populist agenda that helped propel Mr. Trump to the presidency. Some White House aides disparagingly called him “Globalist Gary.” On Tuesday, Breitbart News published an article with the headline “6 Times Globalist Gary Cohn Tried to Derail Trump’s ‘America First’ Agenda.”
Mr. Cohn’s critics said that the timing of his departure made it appear as though he considered the tariff proposals unacceptable, even as he stood by the president after the Charlottesville episode.
“Every White House staffer has their breaking point,” said Ron Klain, a chief of staff to Vice Presidents Joe Biden and Al Gore. “If his breaking point was aluminum tariffs, and not the president’s remarks after Charlottesville, he had the wrong breaking point.”
Mr. George, the Goldman Sachs director, said he did not think Mr. Cohn had to answer for all of the president’s remarks.
“I don’t think he’s tainted at all,” Mr. George said. “He’ll probably take a few months to relax and reflect, and I expect he’ll come back to New York and do something significant in the financial world.”
On Tuesday night, Mr. Trump said he would decide soon on a successor to Mr. Cohn. “Many people wanting the job,” Mr. Trump wrote on Twitter. “Will choose wisely!