Attorney General Loretta Lynch. (Nancy Wiechec/Reuters)

NO DOUBT it’s difficult to refuse a visit with a former president of the United States. Still, Attorney General Loretta Lynch should have found a polite way to excuse herself when Bill Clinton dropped by her airplane, parked next to his at a Phoenix airport Monday. Given that Ms. Lynch has ultimate responsibility for the federal investigation related to Hillary Clinton’s use of a private email server to conduct official business while secretary of state, even an impromptu chat between the attorney general and the candidate’s husband was bound to create questionable appearances — even if its actual content was purely social, as Ms. Lynch maintains and as we believe.

To her credit, Ms. Lynch acknowledged her misstep Friday in an interview with The Post’s Jonathan Capehart at the Aspen Ideas Festival in Colorado. She described the cloud it created over the Justice Department’s objectivity as inaccurate but nevertheless “painful.” Equally appropriately, she said she expected to follow the lead of career prosecutors at the department in deciding what, if any, legal consequences Ms. Clinton should face due to the transmission of classified information via the unsecured server.

Our view of the matter, stated in previous editorials and supported by a fair reading of the law and publicly available evidence, is that Ms. Clinton committed a grave error in judgment, compounded by a willful violation of internal State Department rules designed to ensure records were properly preserved with maximum protection against cybersecurity risks. She has been less than clear and forthright about all of this in her public statements. However, her conduct does not seem to rise to the level of indictable crime, because she did not set up and use the server with the legally requisite criminal intent or even with “gross negligence,” as it has been defined in relevant case law.

The main point now, however, is that the Justice Department needs to get on with telling the public what it has concluded about Ms. Clinton’s culpability. Ms. Lynch’s faux pas is but a relatively minor example of the sort of political accidents that are still waiting to happen as long as this matter remains up in the air. Of far greater moment is the fact that Ms. Clinton is a candidate for president and, indeed, the presumptive Democratic Party nominee. She and, more importantly, the voters who would ultimately judge her deserve some clarity about her legal liability — one way or the other. It appears that a direct interview with the former secretary is one of the last pieces that the Federal Bureau of Investigation needs to finish this puzzle. Both Ms. Clinton and the FBI should make it happen as soon as possible, and then the latter should publish its findings with all deliberate speed.