Editor's Note: (Julian Zelizer, a history and public affairs professor at Princeton University and a CNN political analyst, is the author of "The Fierce Urgency of Now: Lyndon Johnson, Congress, and the Battle for the Great Society." He's co-host of the "Politics & Polls" podcast. The opinions expressed in this commentary are his own.)
(CNN) It feels like President Donald Trump is doing everything in his power to invite the comparison with President Richard Nixon -- and most people don't mean it as a compliment.
President Trump decided to fire the FBI director heading an investigation into the President's campaign and its potential connections to Russia. Historians and political pundits instantly invoked the Saturday Night Massacre, when Nixon ordered the firing of special prosecutor Archibald Cox, who was investigating the Watergate break-in scandal, and the attorney general and his deputy resigned rather than follow orders.
Then, as if President Trump wanted to underline a point, he moved forward with an Oval Office meeting and photo-op with Henry Kissinger, best known as Nixon's national security adviser.
On Friday came the bombshell. In the process of trying to intimidate Comey, Trump warned, via a tweet, that Comey "better hope that there are no 'tapes' of our conversations before he starts leaking to the press."
Nothing is quite as Nixonian as a White House recordings controversy, especially since the impetus for the Saturday Night Massacre was Nixon's refusal to comply with orders to release recordings of White House conversations. Numerous senators from both parties instantly demanded the President release any tapes should they exist. "I am by no means a legal expert," said Virginia Sen. Mark Warner, the top Democrat on the Senate Intelligence Committee, "but this sure seems to have reverberations of past history."
If any recordings exist, their content and the manner in which the White House handles congressional demands to review them will have a much bigger impact than their mere existence. The truth is that we know several presidents secretly recorded their conversations. Starting with President Franklin Roosevelt and continuing through Richard Nixon, presidents -- motivated by everything from a desire to keep accurate records to counter press attacks to a wish to preserve history -- taped telephone conversations and Oval Office meetings. While experts believed the tradition stopped with Nixon, we learned in 2014 that President Reagan recorded telephone conversations with foreign leaders.
As he moves forward, President Trump might want to think about how the revelation of the tapes in 1973 damaged President Nixon. When White House aide Alexander Butterfield revealed to the Senate Watergate Committee in July 1973 that President Nixon had been recording conversations, all hell broke loose. The tapes became pivotal to Nixon's downfall.
President Nixon's efforts to prevent Congress or special prosecutors from seeing the tapes based on executive privilege created a sense among the public and in the halls of Congress that the nation faced a constitutional crisis. Judge John Sirica ruled the tapes be turned over to him for use by a grand jury investigating Watergate. The White House asked the US Court of Appeals to overrule the decision. The White House lost. Even after the Saturday Night Massacre, the 1,300 pages of edited transcripts that Nixon voluntarily shared were shocking -- even though they were sanitized. The transcripts revealed how Nixon had used "dirty tricks" in his campaigns. The constant presence of the phrase "expletives deleted" became a running joke and hurt his standing. "Impeach 'Expletives Deleted'" read the sign of one protester.
Sirica, who had been able to hear some of the actual tapes, knew how much the President had left out in the transcripts. Investigators would discover that there was an unexplained 18½ minute gap during a 1972 conversation about the Watergate break-in, which further fueled suspicion of the President. Finally, the "smoking gun" recording that Congress heard on August 5, a few days after the Supreme Court unanimously ruled the President had to hand over the tapes on July 24, 1974, exposed how President Nixon had attempted to block the FBI investigation. Legislators could hear Nixon tell aide H.R. Haldeman on June 23, 1972, that the CIA "should call the FBI in and say that we wish for the country, don't go any further in this case—period!" That was the final straw for most members of Congress and signaled the end of the Nixon presidency.
The major difference with President Nixon is that no matter how crass the conversations, nothing could be worse than what the current President has already said and tweeted in public. The famous "Access Hollywood" tape did more than anything to push Americans away, but in the end, Trump survived.
At the same time, there is a potentially damaging similarity between Nixon's "smoking gun" tape and what may exist today -- namely, the possibility of attempts to thwart an FBI investigation. If there is evidence President Trump was attempting to obstruct justice in the Russia investigation, this could be devastating. Members of Congress, including Republicans, have become much sharper in their criticism since the President fired Comey and then followed up with comments admitting this was in response to the Russia investigation.
It is still difficult to prove that he intended to obstruct justice. If members were to hear actual conversations with the President plotting out a way to stifle law-enforcement officials and members of Congress, that could be a tipping point that causes many in the GOP to finally break ranks.
Any kind of record that confirms the fears ethics experts in both parties have been raising since his victory could provide enough fodder to turn the conversation toward impeachment. Equally politically devastating would be any kind of recording of President Trump speaking cynically about the core group of supporters who have kept him afloat; that could be the one thing that erodes the steady support he enjoys within the populist Republican base.
President Trump should remember the political and judicial battles over the tapes in 1973 and 1974 proved to be as politically destructive as the tapes themselves. President Nixon's aggressive effort to block access to the material was a powerful factor causing many Democrats and Republicans to conclude this was a president who was out of control, and who needed to be removed from office.
Of course, it could well be that there are no tapes and President Trump has simply been fueling the speculation to distract the attention of the media. If so, then we would be talking about a President who used his bully pulpit to issue a direct threat against a potential witness against him. Not exactly presidential behavior.
If President Trump thinks this issue will go away, he's almost certainly wrong. He's the one who changed the story by bashing the investigation about Russia and got people talking about obstruction of justice. Nixon, who also blasted the investigation about him as partisan hogwash, learned that sometimes, a president can turn out to be his own worst enemy.