Fred Wertheimer is the founder and president of Democracy 21 , a nonprofit, nonpartisan organization that seeks to promote government accountability and integrity. CNN contributor Norman Eisen is a senior fellow at the Brookings Institution and was President Barack Obama's "ethics czar" from 2009-11. He is a former US ambassador to the Czech Republic. The opinions expressed in this commentary are theirs.

(CNN) In an alarming session with reporters this week, President Donald Trump blasted special counsel Robert Mueller and Deputy Attorney General Rod Rosenstein, said the raid on his lawyer Michael Cohen is a "disgraceful situation" and argued that "it's an attack on our country, in a true sense. It's an attack on what we all stand for."

On Tuesday evening, reports were circulating that Rosenstein's job may indeed be at risk. While Mueller is by no means out of the woods, Trump's thinking seems to be that firing the special counsel would kick up too much of a fuss -- so why not replace his supervisor, Rosenstein, with someone more pliable, who can then throttle the investigation?

We have previously explained that firing Mueller would cross a red line. The same would be true if Trump axed Rosenstein or otherwise attempted to shut down or take control of the special counsel investigation. Any of these acts by Trump would deepen his possible liability for obstructing justice (he seems to have forgotten that the firing of FBI Director James Comey triggered the appointment of the special counsel and the investigation, including of potential obstruction, that followed).

The President would be abusing his powers and launching a frontal attack on the rule of law that is a foundational principle of our democracy.

But if it happens, what is to be done? Firing Mueller or Rosenstein would demand an immediate response from the American people and immediate action by Congress.

During the Watergate investigation, the removal of special Watergate prosecutor Archibald Cox in the " Saturday Night Massacre " led to a national uproar. It also ultimately led to the resignation of President Richard Nixon. A similar explosion of protest will occur now if Trump goes down such a path.

The checks and balances of our constitutional system that successfully operated in Watergate provide us with guidance for what we must do in the event that Trump crosses a red line. The three institutions that resolved the Watergate scandal included a continued Watergate special prosecutor investigation, a Senate Select Watergate Committee and the House Judiciary Committee.

In the first instance following Trump's improper firing of Rosenstein, a massive citizen action campaign of which we are a part would demand that the Justice Department and Congress protect the special counsel, his staff and the investigative files, including by passage of long-stalled legislative proposals to that effect. Moreover, whoever replaces Rosenstein in supervising Mueller must guarantee to protect the special counsel's independence. Solicitor General Noel Francisco is currently next in the line of succession.

If the President goes so far as to fire Mueller as well, citizens will demand that a new, independent special counsel be promptly appointed by Francisco. When Watergate prosecutor Cox was fired, a new special counsel, Leon Jaworski, was appointed within 10 days to continue the investigation.

In short, the special counsel's office must be preserved and the staff and work product protected -- and 300,000 Americans have already signed up to protest peacefully and demand all that.

Furthermore, the House Judiciary Committee must immediately begin bipartisan hearings on Trump's obstruction of justice, his abuse of office and his attack on the rule of law.

Additionally the Senate should promptly create a bipartisan select committee, as it did during Watergate, to investigate and hold public hearings on all aspects of the Russian intervention in our elections and Trump's obstruction of justice and abuse of power. A select committee with broad jurisdiction is essential because of the limited jurisdiction that each of the existing Senate committees has to investigate these matters.

Citizens across the nation also must demand that House Speaker Paul Ryan and Senate Majority Leader Mitch McConnell stand up for the rule of law and our system of checks and balances. They must ensure that congressional hearings and investigations begin immediately, and not thwart this from happening. This would be a historic moment where Ryan and McConnell must make a stand. They must stand for country over party, as their predecessors did at the height of the Watergate crisis.

The same kind of institutional checks and balances that resolved the constitutional crisis caused by the "Saturday Night Massacre" can resolve the constitutional crisis that would be caused by Trump firing Mueller, firing Rosenstein or otherwise curbing the essential investigation that is currently taking place.

Trump has attacked the special counsel, the attorney general, the deputy attorney general, the FBI director, the Justice Department and the FBI. Remarkably, he has called the lawful exercise of a search warrant approved by the deputy attorney general and a federal judge an "attack on the country." The President apparently believes he is the country. He is not, as has been the case with every president who preceded him in office.

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Trump repeatedly has shown his disdain for the rule of law and his rejection of our constitutional system of checks and balances. Congress must take all necessary steps to ensure that we remain a government of laws.

This article is adapted, in part, from one published by CNN in August.