WASHINGTON — President Trump’s nominee for general counsel of the Transportation Department, Steven G. Bradbury, is coming under fire by Democrats and human rights advocates for his role in providing legal blessing for waterboarding and other torture techniques used by the Central Intelligence Agency on terrorism suspects during the administration of George W. Bush.

Amid interruptions by anti-torture protesters at his confirmation hearing on Wednesday before the Senate Commerce, Science and Transportation Committee, Democrats grilled Mr. Bradbury about interrogation memos he wrote as head of the Justice Department’s Office of Legal Counsel during Mr. Bush’s second term.

“You lacked the judgment to stand up and say what is morally right when pressured by the president of the United States, and I’m afraid you would do so again,” said Senator Tammy Duckworth, Democrat of Illinois, who wagged her finger at Mr. Bradbury and accused him of having a dangerous “rubber stamp” mentality. “I cannot oppose this nomination strongly enough.”

Mr. Bradbury argued that his job at the Office of Legal Counsel, which is often called O.L.C., was to sort through murky legal issues and that he did not advocate particular policies. He also stressed that the legal landscape was different at the time because Congress had not yet enacted a law requiring intelligence agency interrogators to obey the same rules the military follows.