The banner takeaway from Rod Rosenstein’s confirmation hearing Tuesday was his refusal to say with any certainty that, as deputy attorney general, he would appoint a special prosecutor to investigate Russian interference in the 2016 election. Trump’s pick for the No. 2 job at the Department of Justice—a longtime federal prosecutor from Maryland—wouldn’t have faced questions on this subject under normal circumstances. But with Attorney General Jeff Sessions, Rosenstein’s likely future boss, having recused himself from any investigation into the Trump team’s interactions with Russian officials, he has been thrust into a position of unusual influence over how the issue will be handled by the DOJ.

At his hearing, Rosenstein argued that committing to a special prosecutor before his confirmation would set a dangerous precedent. “I view it as an issue of principle that as a nominee for deputy attorney general, I should not be promising to take action on a particular case,” Rosenstein said. “I believe that if I were to do this in this case, some future deputy attorney general nominee would be … asked to make a similar commitment, and they’d say, ‘Rosenstein did it, why won’t you?’ ”

He also repeatedly pleaded ignorance, explaining that he knew nothing about the status of any Russia-related investigations aside from what he’d read in the media and couldn’t possibly make a ruling as to how the issue should be dealt with until he has an opportunity to weigh the evidence. It was a reasonable enough argument. The Russia situation is extremely opaque, and as these elaborate crib sheets about “what we know and don’t know” from New York and Lawfare demonstrate, we can’t even say for sure which intelligence agencies have been investigating the Trump campaign’s Russia ties, and we certainly don’t have any clarity on what those efforts have turned up.

Realistically, Rosenstein was never going to make a Russia-related promise at Tuesday’s hearing. For all the saber-rattling from Senate Democrats—Sen. Richard Blumenthal says he will do everything in his power to block Rosenstein’s confirmation unless the nominee makes a commitment on the special prosecutor issue—there was just no way Rosenstein would paint himself into that corner. As Rosenstein noted, his colleague Dana Boente—a federal prosecutor who became acting attorney general on Jan. 30, when Trump fired Obama holdover Sally Yates for refusing to defend his immigration ban—has thus far decided against appointing a special counsel. Rosenstein said he was “not in a position to know” whether Boente’s decision is correct or not and wouldn’t be able to reach his own conclusion prior to being confirmed.

There were legitimate political reasons for Blumenthal and his Senate colleagues to pressure Rosenstein on Russia in a public hearing. Doing so allowed them to underscore the DOJ’s key role in getting to the bottom of the mess and to signal to the Trump administration that any in-house—that is, nonindependent—investigation into the matter will inevitably be viewed with skepticism. But if Democratic senators really want to pin Rosenstein down in a way that matters—and they still have an opportunity to do so, as they prepare to submit follow-up queries to Rosenstein in writing—they should ask him a different set of questions. Instead of asking whether he’s prepared to appoint a special prosecutor to look into Trump’s Russia ties, they should ask how exactly he would approach such an appointment if it became necessary. What does Rosenstein think special counsels are for? What does he think his relationship with a special counsel would look like? And most importantly, how much independence would he be willing to guarantee for whomever he appointed to the position?

These questions are crucial, because Rosenstein would have a huge amount of wiggle room to control and supervise any investigation—even a putatively “special” or “independent” one. According to the 1999 regulation that governs the use of special counsels, Rosenstein—as the most senior DOJ official overseeing the investigation—would be able to veto the special counsel on decisions he didn’t agree with, as well as request explanations “for any investigative or prosecutorial step” he or she undertakes. Rosenstein would also be able to remove the special counsel “for misconduct, dereliction of duty, incapacity, conflict of interest, or for other good cause, including violation of Departmental policies.”

Though the regulation does say the special counsel “shall not be subject to the day-to-day supervision of any official of the Department,” the practical reality is that Rosenstein could give the person he appoints as much or as little autonomy as he wants. How he intends to use that power is an open question, and one he should be perfectly capable of answering without having any special familiarity with the details of the Russia case.

At Tuesday’s hearing, only one senator—Amy Klobuchar of Minnesota—had the imagination to ask Rosenstein for his thoughts on the crucial role he’d play in directing a hypothetical investigation.

“It … says that you could overrule a special counsel’s decision,” Klobuchar said, reading from the 1999 regulation. “When would you be willing to overrule a special counsel’s authority?”

Rosenstein responded by harkening back to a post-Watergate law that made it possible for Congress to request the appointment of a truly independent counsel who would, in Rosenstein’s words, “not [be] accountable to the attorney general of the United States.” That law, Rosenstein noted, was allowed to expire in 1999. “Under current law,” he said, “every special counsel we appoint is accountable to the attorney general.”

Rosenstein then got to the point. “The authority that I would give to a special counsel,” he said, “would be whatever authority is appropriate to make sure he or she had the full range of authority to conduct the appropriate investigation that’s required and justified by the facts and law, just like we do in all other cases within the department.”

Klobuchar told me in an interview that she was tentatively pleased with Rosenstein’s answer. “I like that he said ‘full range of authority,’ ” she said. “But I want to know what he meant by some of those other more limiting phrases.”

Those more limiting phrases are indeed a red flag—especially given that Rosenstein didn’t once use the word independent in his answer. Even “full range of authority” is worryingly vague, in that it doesn’t tell us anything about what kinds of decisions Rosenstein would let his special counsel make without his blessing. “Whatever authority is appropriate” is even worse, and in fact makes it sound like Rosenstein would approach the question of independence and autonomy on a case-by-case basis.

It’s not crazy or naïve to feel optimistic that Rosenstein would give a special counsel the proper amount of latitude to do his or her job. For one thing, he would be under considerable political pressure to do so and would be harshly criticized if he didn’t. For another, he has experience as an independent prosecutor himself, from when he worked on the Whitewater investigation under Kenneth Starr. More generally, Rosenstein is widely known as an apolitical, intellectually honest prosecutor who doesn’t let partisan considerations affect his legal judgment. Indeed, Rosenstein is so competent, experienced, and professional that it’s fair to wonder how he got on Trump’s radar in the first place and what Trump’s team thinks it’s getting in bringing him aboard.

But if Rosenstein is truly the principled straight-shooter he’s depicted as in profiles, he should be able to explain with more precision how much authority he’d be willing to delegate to a special counsel. Klobuchar, for her part, said she plans to ask Rosenstein a handful of follow-up questions on this point. Her colleagues on the Judiciary Committee should follow her lead.

In the meantime, Rosenstein’s testimony from Tuesday shouldn’t necessarily be seen as evasive or noncommittal. It’s unfair to expect Sessions’ likely deputy to know what he’ll do once he’s fully briefed on the Russia issue. However, he ought to be able to commit to the idea that special counsels need independence to fulfill their proper function. If he can’t do that, there won’t be any use in him appointing one.