Brett Kavanaugh, President Trump’s second nominee for Supreme Court justice, refused to tell the Senate whether a sitting president should be forced to respond to a subpoena, dismissing the question as “a potential hypothetical.”

“I can’t give you an answer on that hypothetical question,” Kavanaugh told Sen. Dianne Feinstein of California early on the second day of his Senate confirmation hearings.

Feinstein’s question may have been abstract, but it was hardly academic. President Trump is deep in talks over whether and how to submit to questioning by investigators working with special counsel Robert Mueller in their probe of Russian interference in the 2016 election.

Critics of Kavanaugh’s appointment have wondered whether he’d see fit to rule against the man who appointed him to the bench should the standoff with Mueller result in a legal dispute that reaches the Supreme Court.

Kavanaugh himself was also once an important member of the Ken Starr investigation into former President Bill Clinton.

But he said on Wednesday that he had regrets about that entire episode.

“I worked in the independent counsel investigation,” he said. “That was obviously a difficult, controversial moment for our country that I wish hadn't happened. We all wish it hadn’t happened.”

He also said that the terrorist attacks of Sept. 11, 2001, had caused him to reconsider his views about whether presidents should have to face the distraction of an investigation while in office and dealing with matters of national security.

It wasn’t the only time the question of litigation involving a sitting president arose during the hearing. Early on, Kavanaugh also tried to clear the air about a highly controversial comment he’d reportedly made about another president famously subject to investigation: Richard Nixon.

Kavanaugh had reportedly said the Supreme Court decision that forced Nixon to turn over secret White House tapes and eventually led to his resignation, had been wrongly decided against the president.

Kavanaugh said he’d been quoted out of context, and told the committee he strongly supported the decision, albeit within the specific context of the rules regarding independent investigations that were in place at that time. (Those rules have evolved over time.)

On Wednesday, Kavanaugh praised that 1974 ruling as a shining example of judicial independence.

“So that quote is not in context and is a misunderstanding of my position,” Kavanaugh said. “I’ve repeatedly called U.S. v. Nixon one of the four greatest moments in U.S. history.”

But he also specified that five-decade-old decision provides no cookie-cutter example for how he’d rule in the future, and again he declined to give a specific answer.

“My understanding is that you’re asking me to give my view on a potential hypothetical,” he said.