Philip Lacovara was counsel to Watergate special prosecutors Archibald Cox and Leon Jaworski, and also served as deputy U.S. solicitor general responsible for criminal matters, including the “Bronston” case. Lawrence Robbins has been both an assistant U.S. attorney and assistant to the solicitor general. Lacovara is a lifelong Republican; Robbins contributed to and raised money for Hillary Clinton’s presidential campaign. The views expressed are their own.

Attorney General Jeff Sessions made a seemingly false statement under oath during his confirmation hearing. Admittedly, not every potential perjury case gets prosecuted, and Sessions may well have defenses to such a charge. But as lawyers at the Justice Department and attorneys in private practice who have represented individuals accused in such cases, we can state with assurance: Federal prosecutors have brought charges in cases involving far more trivial misstatements and situations far less consequential than whether a nominee to be the nation’s chief law enforcement officer misled fellow senators during his confirmation hearings.

Sessions’s problematic statement involves his response to a question by Sen. Al Franken (D-Minn.) about what he would do as attorney general “if there is any evidence that anyone affiliated with the Trump campaign communicated with the Russian government in the course of this campaign.” Sessions said he was unaware of any such activities, then volunteered, “I did not have communications with the Russians, and I’m unable to comment on it.” In fact, then-Sen. Sessions (R-Ala.), a top Trump campaign adviser, met at least twice during the presidential campaign with Russian Ambassador Sergey Kislyak, The Post revealed.

As any number of witnesses have learned the hard way, it is a federal felony to lie to Congress. Under Title 18 of the U.S. Code, Sections 1001 and 1621, perjury before Congress is punishable by up to five years imprisonment. To prove that offense, a prosecutor would have to establish that Sessions’s answer was false, that he knew it was false when made and that the subject matter of the answer was “material” to the congressional inquiry in which he was testifying.

Those elements all appear to be present. The element of falsity is established by the conceded fact that he did “have communications with the Russians” during the Trump campaign. And there can scarcely be any doubt that the subject matter of Sessions’s answer was highly material to the Senate’s consideration of his nomination. Any suggestion that he participated in the suspected interaction between Trump campaign personnel and the Russian government was, and remains, a matter of grave concern.

That leaves one element: Did Sessions know that his answer was false? He says no, asserting that he understood Franken to be asking only whether he had contact with the Russian government in his capacity as a Trump campaign surrogate. While a jury might accept that defense, there are many reasons to reject it: Sessions’s answer baldly denied any contact. Moreover, Sessions went out of his way to deny contact in response to a question that did not inquire about that subject. By doing so, he preempted an important line of inquiry that might otherwise have been fruitfully pursued.

Certainly there is precedent for a prosecution in this context. Part of the fallout from Watergate included the special prosecutor’s investigation of Richard Kleindienst, who had resigned from his position as attorney general, for alleged false statements during his confirmation hearing before the Senate Judiciary Committee. Kleindienst was asked whether the White House had interfered with a Justice Department antitrust action against the International Telephone and Telegraph Corporation. He stated, “I was not interfered with by anybody at the White House” — but President Nixon and one of his top aides had each called Kleindienst regarding the case. Kleindienst pleaded guilty to a misdemeanor charge for “refus[ing] and fail[ing] to answer accurately and fully” questions at a congressional hearing.

Those facts left no room for any colorable defense on the “knowledge” issue. But when Justice Department officials decide whether to bring a case against Sessions — or, more appropriately, when an independent counsel is appointed and resolves that question — this must be done against the backdrop of other perjury cases that the department has chosen over the years to bring. And the department has prosecuted individuals who advanced defenses very similar to Sessions’s arguments here, often where there was far less at stake.

Years ago, for example, one of us (Robbins) represented a defendant named John Patrick Dowd, accused of lying to a grand jury. Dowd was president of a company that had leased a vessel that had dumped 13,500 tons of Philadelphia incinerator ash into the sea. There was no evidence that Dowd was personally involved in the dumping, but his grand jury testimony led to a perjury indictment. Dowd was acquitted of lying to the grand jury when he testified that he didn’t know where the ash went. Yet he was convicted for his negative response to the question: “You had no idea?” Thus, even a question and answer far vaguer and more ambiguous than the Franken-Sessions exchange were deemed sufficient to justify prosecution.

Or take the classic case of vague questioning: Bronston v. United States. Samuel Bronston had placed his movie production company into bankruptcy and was being questioned about his and the company’s finances. He was asked about, and denied, having any accounts in Swiss banks. Then the obvious follow-up — “Have you ever?” — to which Bronston replied: “The company had an account there for about six months.” What Bronston neglected to mention was that he had a large personal Swiss bank account that he closed when he filed to place his company in bankruptcy.

The Supreme Court held that although his responses may have been deceptive and intended to mislead, they did not constitute perjury because they were literally true, and it was the fault of the questioner that he failed to pursue the inquiry further. The Sessions’s situation presents exactly the opposite scenario: Sessions’s response appears to be both literally false and comprehensive, leaving nothing open for further inquiry regarding the nature of his contacts with the Russian government during the presidential campaign.

A government that has been willing to prosecute relatively small and questionable instances of falsity in connection with matters of comparatively minor importance should have difficulty explaining why Sessions’s testimony would receive a free pass.