WASHINGTON >> The disclosure that Russia’s ambassador to the United States spoke twice with Attorney General Jeff Sessions last year, even though Sessions testified at his January confirmation hearing that he “did not have communications with the Russians,” has set off a new round of political furor in Washington, this time with legal overtones.

After Republicans began joining Democrats on Thursday in calling upon Sessions to recuse himself from overseeing any criminal investigation related to Russian meddling in the 2016 election, the attorney general announced that he would step aside from any current or future cases related to the campaign. As a senator, Sessions was a top campaign adviser to President Donald Trump.

But some Democrats called for giving the investigation even greater independence. Others accused Sessions of lying under oath and called for his resignation and a criminal investigation. The developments have heightened interest in several related legal issues.

— What does it mean for the attorney general to recuse himself?

Generally, U.S. attorneys directly oversee criminal investigations. In a case that raises politically sensitive issues, the attorney general normally would be briefed on proposed major decisions — like whether to subpoena a high-profile witness or bring charges — and could overrule them. By recusing himself now, Sessions is responding to concerns that exercising that role, in light of his ties to the Trump campaign, would call into question the impartiality of the justice system.

— Who replaces the attorney general after a recusal?

The deputy attorney general steps into the shoes of the attorney general to make decisions about that particular investigation. The acting deputy attorney general is Dana J. Boente, the U.S. attorney for the Eastern District of Virginia, whom Trump temporarily elevated last month after firing Sally Q. Yates, who had been the deputy attorney general. Trump has nominated Rod J. Rosenstein, the U.S. attorney for Maryland, to be deputy attorney general, and he would replace Boente if confirmed.

— Can a special prosecutor or an independent counsel be appointed?

No, because the law that created that type of prosecutor expired.

During the Watergate “Saturday Night Massacre,” President Richard M. Nixon ordered the firing of the prosecutor running the investigation into his White House. As part of the reforms afterward, Congress created a new type of prosecutor to look into high-level executive branch wrongdoing while shielded from political interference. This position was called a special prosecutor at first and later independent counsel. The law set criteria for an attorney general to request a three-judge panel to appoint such a prosecutor, who would be subject to the judges’ supervision and could not be fired by the president or his appointees.

While the Supreme Court upheld the arrangement as constitutional, critics said it permitted a prosecutor to run amok. Republicans learned to hate the arrangement during the Iran-Contra investigation into the Reagan administration, and Democrats did during the Whitewater and Monica Lewinsky investigations into former President Bill Clinton. When the law expired in 1999, Congress did not renew it.

— Could there instead be a special counsel?

Yes, Boente could appoint one of these.

Special counsels are empowered to run an investigation with greater autonomy than a U.S. attorney normally enjoys. But they are still ultimately subject to the control of the attorney general — and the president — who can overrule their decisions or fire them. This position dates to 1999, when the Justice Department issued new regulations to create it after the independent counsel law expired.

The regulations say special counsels “shall not be subject to the day-to-day supervision of any official of the department” and generally decide on their own “whether and to what extent to inform or consult with the attorney general or others within the department about the conduct of his or her duties and responsibilities.”

— Did Sessions commit a crime?

In a letter to the FBI and the Justice Department, Democrats on the House Judiciary Committee asked for “an immediate criminal investigation into these statements, which could potentially implicate a number of criminal laws, including lying to Congress and perjury.”

But it is exceedingly unlikely that the Justice Department will bring charges against the attorney general — and not just for political reasons. To violate statutes that criminalize lying to Congress and perjury, it is not enough to say something that turns out to be demonstrably false. Rather, the speaker must have intentionally lied. That can be very difficult to prove beyond a reasonable doubt.

Sessions has said that while some people think he made a false statement, that was “not my intent.” Rather, he said, his answer was “honest and truthful as I understood it at the time” because the context of the question was the allegation that the Trump campaign and the Russian government were exchanging information. He said he understood his meetings with the Russian ambassador to be linked to his role as a senator, not his role as a campaign surrogate.

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