Only one other US president has ever acted as desperate as Donald Trump

President Donald Trump gestures as he speaks at a rally at Olentangy Orange High School in Lewis Center, Ohio. Photo / AP

President Donald Trump is acting with a desperation I've seen only once before in Washington: 45 years ago when President Richard Nixon ordered the firing of special Watergate prosecutor Archibald Cox. Nixon was fixated on ending the Watergate investigation, just as Trump wants to shut down the special counsel's investigation into Russian interference in the 2016 election.

A lesson for the president from history: It turned out badly for Nixon. Not only could he not derail the investigation, but also, 10 months later, he was forced to resign the presidency.

President Donald Trump gestures as he speaks at a rally at Olentangy Orange High School in Lewis Center, Ohio. Photo / AP

In fact, in some ways, Trump is conducting himself more frantically than Nixon, all the while protesting his innocence. Nixon fought to the end because he knew that what was on the tape recordings that the prosecutor wanted would incriminate him. We don't know what Trump is hiding, if anything. But if he is innocent of any wrongdoing, why not let special counsel Robert Mueller do his job and prove it?

In October 1973, Nixon ordered Attorney General Elliott Richardson to fire Cox. Richardson refused and resigned. As deputy attorney general and next in line, I was ordered by the president to fire Cox; I also refused and resigned. Cox was finally fired by Solicitor General Robert Bork. The result is what came to be known as the Saturday Night Massacre.

Neither Richardson nor I saw any justifiable reason for Cox's dismissal. When it became clear that Cox would not give up his pursuit of the Oval Office tapes, Nixon took the only action he could to protect himself: He tried to get rid of the man charged with investigating him.

Nixon was desperate. His goal was to shut down the Watergate investigation by ridding himself of Cox. Instead, Nixon got Leon Jaworski, the highly respected former president of the American Bar Association. Nine months later, the Supreme Court handed down a unanimous decision forcing Nixon to release the tapes that proved his guilt. Shortly thereafter, the president resigned.

Not only was that Saturday night the beginning of the end of the Nixon presidency, but it also accelerated the growing wave of political cynicism and distrust in our government we are still living with today. One manifestation of that legacy: a president who will never admit he uttered a falsehood and a Congress too often pursuing only a partisan version of the truth.

Trump might attempt to shut down the Mueller investigation, but if he fires the special counsel, he could face the same result Nixon faced. He would look like a president with something to hide. He would unleash forces bigger than one man, because Americans believe no one is above the law, not even the president.

Former President Nixon. Photo / AP

Nixon was brought down by his disrespect for the rule of law. The hundreds of letters that I received after my refusal to fire Cox enshrined this thought in my head for the rest of my life.

It's hard to believe that, 45 years later, we may be in store for another damaging attack on the foundations of our democracy. Yet the cynical conduct of this president, his attorneys and a handful of congressional Republicans is frightening to me and should be to every citizen of this country. We are not playing just another Washington political game; there is much more at stake.

The vehemence and irresponsibility of the rhetoric attacking the Mueller investigation tear at the very structure of our governance. Men who have sworn to use and protect our institutions of justice are steadily weakening them. Should the president finally decide to fire Mueller and put in place someone who will do his bidding, the country could be thrown into a political crisis that would scar our democracy and further erode the trust of our people in our governmental institutions.

We need leaders who tell the truth. This is not now happening. Mueller is living up to his superior reputation as a model public servant. His is a search for the truth; we should not complicate his job. Support him, and when he has finished his work, listen to what he has found.

What Mueller unearths will guide our next steps and will strengthen our trust in our institutions - including the one we are now using to find the truth. I hope the president at last studies the lessons of a history I lived - and that he heeds its warning.

Ruckelshaus served as acting director of the Federal Bureau of Investigation and as deputy attorney general in 1973. He was also administrator of the Environmental Protection Agency from 1970 to 1973 and 1983 to 1985.