Six days after the Watergate office complex break-in, the “smoking gun” tape recorded on June 23, 1972, memorialized a conversation between President Nixon and his chief of staff, H.R. Haldeman. In it, Haldeman advised Nixon that “the problem” they faced was that the “FBI is not under control” and the director of the Bureau, L. Patrick Gray, “doesn’t know exactly how to control this.” According to Haldeman, the FBI investigation seemed to be heading in “some directions we don’t want it to go.”

So Haldeman presented the president with a solution. What if Haldeman, along with presidential adviser John Ehrlichman, directed the director and deputy director of the CIA, Richard Helms and Vernon Walters, to tell Gray to drop the investigation because it would otherwise disclose national security matters?

Nixon quickly agreed. “Good deal,” Nixon said, “play it tough.” After all, “that’s the way they play it, and that’s the way we are going to play it.”

The rest, as they say, is history: Special Counsel Archibald Cox subpoenaed the tape, prevailed unanimously in the Supreme Court, and on August 5, 1974, a transcript of the June 23 tape was publicly released.

In short order, the 10 Republican members of the House Judiciary Committee announced that they would now vote in favor of impeachment. Senators Barry Goldwater and Hugh Scott, along with the House Minority Leader, John Rhodes, thereafter went to the White House to advise President Nixon that he no longer commanded sufficient Republican support to withstand an impeachment trial. Four days later, on August 9, 1974, Nixon resigned.

Too bad he didn’t have Bill Barr as his attorney general at the time.

In his May 1 testimony before the Senate Judiciary Committee, Attorney General Barr repeatedly invoked the broad proposition that when a president exercises his authority under Article II of the Constitution in a “facially innocent” fashion, a prosecutor cannot reasonably find the corrupt intent needed to charge obstruction of justice. According to Barr, “most of the episodes” detailed in Volume II of the Mueller Report involved precisely such exercises of presidential discretion.

These “facially innocent episodes” presumably include President Trump’s attempts to discharge Mueller; his efforts to constrain the scope of the Mueller inquiry only to future Russian influence; his repeated instructions to the White House counsel to lie to the public and create false and misleading documents; and his (successful) discharging of FBI Director Comey for the self-confessed purpose of derailing the Russia Investigation.

This aggressive theory of executive power—espoused mainly by a handful of lawyers, most of whom serve mainly as TV personalities these days—was definitively refuted in Volume II of the Mueller Report itself. As Mueller explained, applying an obstruction statute to the president, even when he exercises core Article II authority, is entirely constitutional whenever the president is acting for such “personal purposes” as “shielding himself from criminal punishment, avoiding financial liability, or preventing personal embarrassment.” In such cases, Mueller added, holding the president accountable “furthers, rather than hinders, the impartial and evenhanded administration of the law.”

Barr’s contrary view is essentially a form of presidential immunity. After all, there is almost nothing a president can do, (short of shooting someone in the middle of Fifth Avenue) that cannot somehow be construed as an exercise of Article II power.

But as the Watergate “smoking gun” tape illustrates, Barr’s Article II defense is also deeply ahistorical. Nixon, no less than Trump, believed that he was being hounded by his political enemies. Nixon, no less than Trump, believed himself—to quote Barr—to have been “falsely accused” of the underlying Watergate offense. Nixon, in fact, held precisely the subjective beliefs that, in Barr’s view, should have rendered him immune from obstruction charges.

As Nixon asserted in his 1977 interview with David Frost, “I didn’t have [the] corrupt motive” required for an obstruction charge. Instead, he contended, “my motive was pure political containment, and political containment is not a corrupt motive.”

Moreover, like Trump—who, Barr tells us, believed there was no underlying offense—Nixon claimed that he “didn’t believe that John Mitchell was involved,” or for that matter, that “anybody else was.” So acting to derail the Watergate investigation was simply an effort to “contain it politically,” which is “a very different motive” from “attempting to cover up criminal activities.”

Indeed, unlike Trump—who openly exhorted the Russians to hack Secretary Clinton’s emails; helped his son concoct a false story to conceal the Russian outreach at Trump Tower; and encouraged WikiLeaks in its dissemination of unlawful Russian document dumps—Nixon, by all accounts, actually was innocent of the activities at the heart of the underlying investigation in Watergate.

So why not tell FBI Director Gray to drop the investigation? Gray, after all, was every bit Nixon’s subordinate as Comey, Mueller, Sessions, and McGahn were subordinate to Trump. Nixon had the same Article II authority as Trump did to direct Gray to knock it off. Yet, Nixon’s exercise of that “facially innocent” authority was not defended by the Department of Justice, turned most of the Republican members of Congress against him, and effectively ended his presidency.

It won’t end Trump’s. In our time, the smoking gun evidence, to borrow from Trump’s Twitter feed, is little more than a “smocking gun.”