Mr. Josten is not leaving because of the changing landscape and the arrival of President-elect Donald J. Trump. He says he just sees it as a good moment to turn over his responsibilities to successors he has helped recruit. But he does not dispute that the chamber has become a punching bag for some on the right who view establishment entities and their defense of institutions such as the Export-Import Bank as a big part of the problem in Washington.

He attributes the criticism of the bank, which provides government help to exporters, to a lack of understanding of international markets. And he sees the assault on the chamber by advocacy groups as a way to tap into public anger — and wallets.

“You need something to sell against to raise money, to be frank,” he said. “If you look at Trump’s campaign, he embodied that divisiveness, fear and anger in the American people. We are on the other side of that and we are a big target.”

Mr. Josten is more concerned with the trend toward one party going it alone legislatively, using its power to impose its priorities on the other as the Democrats did with the health care law and Republicans are threatening to do by repealing it. That approach is not sustainable in the long run, he said.

“If you want durability and lasting law, the only way to really achieve it is to engage both sides of the aisle and reach an outcome that the president, regardless of party, will sign because of the product itself,” he said.

He sees a current political and legislative climate marked by a certain inflexibility and intransigence that is not conducive to compromise and ends with little being accomplished.

“From time to time, you work with your adversaries,” said Mr. Josten, who became the chamber’s chief lobbyist in 1994, as the organization faced a membership revolt over the chamber’s initial endorsement of key elements of the Clinton administration’s health care proposal. “You’ve got to be able to separate certain things at certain times and do what is right for your constituents. I think it just became harder and harder for the politicians to do that and I think that has had an impact on all of us in town.”