Under insistent questioning from Democrats, deputy attorney general nominee Rod J. Rosenstein refused to commit Tuesday to appoint a special counsel to oversee investigations of Russian meddling in the presidential election — though he stressed that he did not yet know the facts of the matter.

At a tense Senate Judiciary Committee confirmation hearing that lasted more than 3 1/2 hours, Rosenstein said that he was “not aware” of any reason he would not be able to supervise such probes.

“You view it as an issue of principle, that I need to commit to appoint a special counsel in a matter that I don’t even know if it’s being investigated,” he told Sen. Richard Blumenthal (D-Conn.), who had vowed to try to block his nomination should he not make such a commitment. “And 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.”

[Justice Department nominee at center of partisan battle of Russia allegations]

Rosenstein is a respected prosecutor who has served in both Democratic and Republican administrations. But on Tuesday, Democrats and Republicans essentially turned him into a lightning rod, pressing him for answers on how he would handle any probes of Russian meddling in the U.S. election or Trump associates.

Last week, Attorney General Jeff Sessions announced that he was recusing himself from any campaign-related investigations after The Washington Post reported that he had met with the Russian ambassador twice during that campaign and had not disclosed that fact at his own confirmation hearing. That would mean supervision would fall to Rosenstein if he is confirmed.

Rosenstein said he would handle it “the way I would handle any investigation.”

Asked whether he had any contact with Russian officials, he said that throughout his career, he has spoken to lawyers and judges visiting from foreign countries at events, and that “it’s certainly possible there may have been Russian officials there.” But he said he did not “recall any such meetings” with Russian officials. He also said he has not talked with Sessions about Russian contacts, and he sought to assure legislators that he would act in the best interests of the United States.

“I don’t know the details of what, if any, investigation is ongoing, but I can certainly assure you if it’s America against Russia, or America against any other country, I think everyone in this room knows which side I’m on,” he said.

Perhaps the most heated exchange came after Sen. Al Franken (D-Minn.) lambasted Sessions for not disclosing his meetings with the Russian ambassador. It was Franken who asked Sessions at his own confirmation hearing in January what he would do if it was found that anyone affiliated with the Trump campaign had communicated with the Russian government.

Sessions responded, “I have been called a surrogate at a time or two in that campaign, and I did not have communications with the Russians.”

Franken posed the same question to Rosenstein, who responded, “If there is predication to believe that such communication was in violation of federal law, Senator, I would ensure an appropriate investigation.” The Minnesota Democrat then criticized Sessions for his response and suggested that his letter to the committee Monday insisting it “was correct” was inadequate.

“He answered a question I didn’t ask, and for him to put this in his letter as a response is insulting, and he should come back and explain himself,” Franken said.

[In update to Congress, Sessions insists he was ‘correct’ to say he had no communication with Russians in campaign]

Senate Judiciary Committee Chairman Charles E. Grassley (R-Iowa) fired back that Franken had asked a “gotcha question,” eventually pounding his gavel to cut Franken off.

“It was not a gotcha question, sir,” Franken exclaimed.

“It was, from the standpoint that he didn’t know what you were asking about,” Grassley said.

Sen. Lindsey O. Graham (R-S.C.) grilled Rosenstein about Trump’s weekend tweet accusing then-President Barack Obama of wiretapping him before the election. Rosenstein responded: “I don’t think it’s appropriate for me to share my reaction, Senator. It has no bearing on my work.”

He later added, “If the president is exercising his First Amendment rights, that’s not my issue.”

[Meet Rod Rosenstein, the official poised to oversee probe into Russian interference in 2016 race]

Grassley opened the hearing by declaring that any talk of a special counsel was “premature” and that Rosenstein was well equipped to handle sensitive investigations.

“There are times when special counsels are appropriate,” Grassley said. “But it’s far too soon to tell at this time. And even if there were evidence of a crime related to any of these matters, once confirmed, Mr. Rosenstein can decide how to handle that matter. I know of no reason to question his judgment, his integrity or his impartiality.”

Grassley and others, including Sen. Orrin G. Hatch (R-Utah), repeatedly brought up Loretta E. Lynch, the attorney general during the Obama administration, noting that she did not recuse herself from an investigation into Hillary Clinton’s email practices, even after reports about a tarmac meeting she held with Bill Clinton.

“My Democratic friends have nothing to say about that,” Hatch said. He added: “This kind of double standard makes it look like partisan politics.”

Although Lynch stopped short of recusing herself, she did agree to accept recommendations in the Clinton probe from the career prosecutors and FBI agents leading that investigation.

Sen. Dianne Feinstein (D-Calif.), the committee’s ranking Democrat, said that a fully independent investigation on Russia was needed to avoid “even the appearance of a conflict of interest.”

“To be clear, I do not say this because I question the integrity or the ability of Mr. Rosenstein,” Feinstein said. “I do not.”

She later warned, “There is a real danger, I believe, that the Justice Department could become politicized.”

Sen. Chris Van Hollen (D-Md.), who introduced Rosenstein, said that he had conveyed to Rosenstein that if FBI Director James B. Comey had asked the Justice Department to issue a statement rebutting Trump’s claim that Obama had ordered a wiretap of him before the election, “then the Justice Department has a duty to let the public know the truth.”

Under later questioning from Sen. Amy Klobuchar (D-Minn.), Rosenstein declined to address those particular events, though he said he would “certainly consider” the FBI director’s views in whether to issue a public statement.

Thelongest-serving U.S. attorney, Rosenstein, 52, has worked on sensitive cases in the face of political pressure, according to attorneys he has worked with during his nearly three decades in the department.

A bipartisan group of 127 former U.S. attorneys, who were appointed by and served under various presidential administrations, sent a letter Monday to the Senate Judiciary Committee supporting Rosenstein’s confirmation.

He began working as a trial attorney in the public integrity section of President George H.W. Bush’s Justice Department in 1990 after graduating from Harvard Law School and clerking for Judge Douglas H. Ginsburg of the U.S. Court of Appeals for the District of Columbia Circuit. Soon afterward, President Bill Clinton’s deputy attorney general hired Rosenstein to be his counsel.

During the Clinton administration, Kenneth W. Starr tapped Rosenstein to be his associate independent counsel on the investigation into the business dealings of the Clintons and their associates in the Whitewater Development Corp. Rosenstein stayed on into the George W. Bush administration, and in 2005, Bush appointed him U.S. attorney for the District of Maryland, where he remained through the Obama administration.

Senators also considered the nomination of Rachel Brand on Tuesday to serve as associate attorney general, the third-highest position in the Justice Department.