The deputy attorney general declined Wednesday to pledge full independence to the special counsel investigating the ties between Russia and Team Trump, raising new questions about the future of the probe.

Rod Rosenstein recently named former FBI Director Robert Mueller to lead that investigation, after the firing of FBI director James Comey—and allegations that the president was interfering into a probe of his own administration. But during a hearing of the Senate Intelligence Committee, Rosenstein pointedly declined to say that he would fully empower Mueller to run an independent investigation.

It was one of a number of incidents during Wednesday's hearing that cast a pall over the Trump-Russia case.

Sen. Kamala Harris, a California Democrat and previously her state’s attorney general, repeatedly pressed Rosenstein to affirm he had or would use his statutory power to make Mueller “fully independent” from the Justice Department. Rosenstein is the acting attorney general over the Mueller probe after Jeff Sessions’ recusal. But Rosenstein, who until the Comey firing was an official who enjoyed widespread respect, dodged the question and suggested it was irrelevant.

“Under the regulation, [Mueller] has, I believe, adequate authority to conduct this investigation. And your ultimate check, Senator, is, number one, the integrity of the people involved in the investigation; but number two, the fact that if he were overruled or if he were fired, we would be required under the regulation to report to the Congress, and so I believe that is an appropriate check,” Rosenstein said.

“I realize that theoretically, anybody could be fired and so there’s a potential for undermining an investigation, but I am confident, Senator, that Director Mueller, Mr. McCabe, and I, and anybody else who may fill those positions in the future will protect the integrity of that investigation. That’s my commitment to you.”

In effect, Rosenstein was saying: trust me. Trust me to be independent.

Rosenstein, however, drafted a memo that Trump relied upon to fire the FBI director investigating him, something that made legal observers directly question his integrity. After the White House initially insisted it was merely following Rosenstein’s guidance, Trump told NBC’s Lester Holt: “regardless of recommendation, I was going to fire Comey knowing there was no good time to do it. And in fact, when I decided to just do it, I said to myself -- I said, you know, this Russia thing with Trump and Russia is a made-up story.”

According to Comey, Trump on March 30 called the then-director to say the Russia investigation, whose existence Comey had confirmed 10 days earlier, was casting a “cloud” over his presidency. Comey will testify on Thursday that Trump ‘asked what we could do to ‘lift the cloud.’”

Nevertheless, Rosenstein told top committee Democrat Mark Warner: “If anyone obstructs a federal investigation, it would be a subject of concern. I don’t care who they are.”

Karen Greenberg, director of the Center on National Security at Fordham Law School, said Rosenstein was once again allowing himself to be used by Trump, but “this time, with his eyes open.”

With an active investigation into Trump then run by Comey, Greenberg continued, “It’s not OK to fire the director of the FBI. It’s not OK. And we have not reacted as a country in the way we need to. It’s not just obstruction of justice, it’s something every piece of the statute about the FBI director’s independence is supposed to to guard against. Rosenstein, by getting with the program, is making it harder for us to see how egregious what happened was.”

It wasn’t the only time Rosenstein found himself in questionable territory on Wednesday. The deputy attorney general—along with his fellow panelists director of national intelligence Dan Coats, National Security Agency chief Mike Rogers, acting FBI director Andrew McCabe—also refused to say whether Donald Trump had asked them to stifle the FBI investigation into the Russia question.

Over two hours in a hearing before the Senate intelligence committee, the top officials claimed such information would be too sensitive to publicly divulge to Congress. It’s an explanation classification experts said was bogus.

The non-answers concerned a grave topic: the appearance or reality of the president of the United States obstructing an investigation into his team’s connections to a hostile foreign power. Frustration with the four senior officials boiled over, from Republicans, Democrats and the panel’s only independent.

Rogers, a Navy admiral, testified that he would not answer questions about Washington Post reporting saying Trump had requested he and Coats stifle now-fired FBI director James Comey’s probes and help Trump publicly push back against it. When Rogers was pressed about the basis for his refusal – particularly since the White House had not exercised executive privilege – he replied, “because I feel it is inappropriate.”

Maine independent Angus King shot back: “What you feel isn’t relevant, admiral. What you feel isn’t the answer.”

Again and again, Rogers and Coats, two of the senior most U.S. intelligence officials, refused to say if Trump had made any such request. Rogers instead testified that he did not “feel pressured” by anyone to commit an illegal and unethical act, which several senators pointed out was a dodge. Coats said simply that his discussions with the president typically involved classified information and insisted than an open hearing was an improper forum for an answer.

Florida Republican Marco Rubio clarified “not asking for classified information. I’m asking whether there was influence by anyone.”

It was to no avail. Rosenstein, whose memorandum about Comey’s handling of the Hillary Clinton investigation provided Trump with a pretext for firing the FBI director, joined with Comey’s interim replacement, McCabe, in saying they had to be “careful” not to get in the way of special counsel Mueller’s Trump-Russia probe.

But, significantly, they were not able to definitively state that answering questions about potential Trump interference would indeed get in the way of Mueller’s inchoate investigation—something that would indicate Mueller will look at obstruction of justice as well as the facts of the Trump-Russia allegations.

Steven Aftergood, an expert on classification at the Federation of American Scientists, said that the four senior officials had not provided any legitimate basis for declining to answer the Senate’s questions, particularly as conversations about presidential interference with an ongoing investigation are not in fact classified.

“What was being asked was about conversations these individuals had with the president and expressing preference for how the administration wanted to go forward. No, it’s hard to see any national security aspect to that,” said Aftergood, who said it seemed more like they were “camera shy” than relying on a valid basis for stonewalling their Senate overseers.

“They were hemming and hawing and declining to answer. But they declined to answer in a way that suggested that they had something to say that they weren’t saying. So it’s both frustrating and enticing,” Aftergood said.

Rogers and Comey suggested that they would be more forthcoming in a later closed session. But Rogers intimated it was possible that the White House would exercise executive privilege over that round of testimony. When he asked the White House if it would try to block his answers, Rogers said, “I didn’t get a definitive answer.”

Comey will testify on Thursday before the same panel in the most highly anticipated congressional hearing in recent memory – possibly since Comey’s own career-making 2007 testimony about George W. Bush’s efforts to protect warrantless surveillance. Wednesday’s hearing, which ostensibly covered an expiring surveillance authority, was a mere opening act. But hours before it began, Trump announced his pick to succeed Comey at the FBI.

Asked if the Senate panel was content with the senior officials’ non-responses, Oklahoma Republican James Lankford said: “ I don’t think anybody was. There’s still questions that are hanging out there and it’s appropriate for us to continue to have questions, and we’re gonna work to get answers on it.”

As the hearing wrapped up, Rogers, normally a figure who receives deferential treatment on Capitol Hill, remarked, “ Some days, I sure wish I was an ensign on the bridge of that destroyer again.”

-- with additional reporting by Andrew Desiderio