We’re here again. A powerful and determined president is squaring off against an independent investigator operating inside the Justice Department. Robert Mueller’s mission is a comprehensive look at Russian meddling in the 2016 election — and any other crimes he uncovers in the process. President Trump insists it’s all a “witch hunt” and an unfair examination of his family’s personal finances. He constantly complains about the investigation in private and reportedly asked his White House counsel to have Mueller fired. No wonder many people are making comparisons to the “Saturday Night Massacre” of 1973, when President Richard Nixon fired special prosecutor Archibald Cox, and Attorney General Elliot Richardson and Deputy Attorney General William Ruckelshaus resigned.

We covered that eerily similar confrontation for The Washington Post 45 years ago. Nixon didn’t know it at the time, but the Saturday Night Massacre would become a pivot point in his presidency — crucial to the charge that he’d obstructed justice. For him, the consequences were terminal. A retelling of the episode, adapted from “The Final Days,” as we called our book on the president’s last year, can illuminate the stakes.