“He’ll be addressing a lot of key issues,” Senator Rob Portman, Republican of Ohio and a committee member, said, expressing confidence in Mr. Risch. Besides, Mr. Portman added, “members are independent actors, and we’re all going to speak up and let our views be known.”

Senator Chris Coons, Democrat of Delaware and another committee member, hit on the same point: “I understand that Chairman Risch has a different style and approach perhaps than Chairman Corker did, but I am determined that the committee will be no less effective.”

Some foreign policy experts say even Mr. Corker was derelict in his duty to turn acerbic comments into real oversight or legislation. Under Mr. Risch, even the words might go silent. And that will have real consequences.

Leveraging the committee’s oversight power is “a critical element of getting to the right place,” said Wendy R. Sherman, an under secretary of state and acting deputy secretary of state under President Barack Obama.

“I’m not saying that Senator Risch should be combative with the president, but where there is disagreement, we rely on the U.S. Senate,” Ms. Sherman said. “They can take the long view, and for them to defer to the president on everything really undermines the strength of that committee and the historic role that it’s played.”

Stewart M. Patrick, a senior fellow at the Council on Foreign Relations and former policy staffer at the State Department under President George W. Bush, said, “It’s not enough simply to make, as Bob Corker did pretty frequently, made-for-TV sound bites expressing alarm or discomfort about U.S. policy unless there’s going to be substantive hearings about the wisdom of those choices.” He added, “The danger with Mr. Risch is that we are going to get neither expressions of alarm when the administration is off track, nor effective oversight.”

Allies of the new chairman describe him as a workhorse, not a showhorse. But on policy, Mr. Trump has a friend at the helm of the Foreign Relations Committee. Mr. Risch has broken with the president on occasion, joining his colleagues to protest Mr. Trump’s appetite for leaving the Atlantic alliance, and taking an aggressive stance on Russia.