WASHINGTON — In another time, in another Washington, this might be the moment that changed the trajectory of the presidency. A former national security adviser confirms that the president, despite his denials, conditioned security aid to a war-torn ally on its cooperation against his domestic rivals, the issue at the heart of his ongoing impeachment trial.

At first glance, John R. Bolton’s account of President Trump’s private remarks sounded like an echo of the so-called smoking gun tape that proved President Richard M. Nixon really had orchestrated the Watergate cover-up and ultimately forced him from office. By the end of Monday, the revelation appeared to make it more likely that the Senate will agree to hear witnesses at the trial.

But this is Mr. Trump’s era and Mr. Trump’s Washington, and the old rules do not always apply anymore. The reality show star who was elected president even after he was captured on an “Access Hollywood” tape boasting about sexual assault has gone on to survive one politically charged furor after another during his three years in the White House, proving more durable than any national politician in modern American history.

So will this be a Watergate-style turning point or just one more disclosure that his critics consider validation without changing other minds? Will it be another smoking gun or another “Access Hollywood”?