Newton N. Minow, senior counsel at the law firm Sidley Austin, was chairman of Public Broadcasting Service from 1978 to 1980 under President Carter and was appointed to presidential commissions and a Defense Department panel for the George H.W. Bush, Clinton and George W. Bush administrations. He also served as an informal adviser to President Obama, who awarded him the Presidential Medal of Freedom.

Dear Presidents Jimmy Carter, George H.W. Bush, Bill Clinton, George W. Bush and Barack Obama:

I am privileged to have known and worked with each of you and your administrations. I know how deeply you all love our country.

Our nation is blessed to have the five of you and your invaluable experience in the Oval Office — a total of 32 years with your steady hands on the nuclear codes. The time has come to use this unique asset to help the nation deal with our present situation.

Most of us now have very short attention spans. The news comes at us 24/7. One crisis immediately follows another, and we forget what has happened even one month ago. We need to keep reminding ourselves what has happened since President Trump took office:

●The president revealed highly classified information to foreign leaders for no apparent strategic purpose.

●He ignored ethical principles by not fully divesting from his businesses while in elected office.

●He waffled on condemning white- ­ supremacist, Nazi and Ku Klux Klan protesters.

●He pardoned former Arizona sheriff Joe Arpaio, who was convicted of criminal contempt for violating a direct court order to stop racially profiling people.

●He fired FBI Director James B. Comey, who was supervising an investigation into the conduct of his presidential campaign.

●He persisted in condemning and seeking to discredit judges, science, the news media and, indeed, any source of authority that disagreed with him.

●He has insulted our allies abroad — as well as the leadership of his own party.

And then came two shocking and alarming warnings about the president's stability. The first was from Bob Corker (R-Tenn.), chairman of the Senate Foreign Relations Committee, who said the president "has not demonstrated he understands the character of this nation" and "has not yet been able to demonstrate the stability, nor some of the competence that he needs to demonstrate in order to be successful."

Second, former director of national intelligence James R. Clapper Jr. said: "I really question his ability to — his fitness to — be in this office, and I also am beginning to wonder about his motivation for it."

These red flags alerted us to be deeply concerned about our current president's stability. News reports indicate that North Koreans, confused by contradictory messages from Trump and other members of his administration, are seeking out former American public officials to clarify American policy. Wars often start through confusion, miscalculation and failures of communication.

Millions of Americans are talking with friends and relatives and wondering what could happen, but there has been no serious, sustained public examination of the challenge to our nation.

That is why I believe that the five of you, working together, can and should supply the leadership our country is missing. Some of you have already spoken out against Trump's actions. But together, as a bipartisan group, you could have a greater impact.

You all know that the Constitution and rule of law are only as good as the men and women who enforce them. You know from your time as president what it means to have your hands on the nuclear codes. And you know that the nation cannot risk having an unstable hand.

When our Constitution was enacted, a Philadelphian asked Benjamin Franklin, "What have you given us, a monarchy or a republic?" He replied, "A republic, if you can keep it." Americans want to keep our republic, our Constitution and our way of life. People around the world, looking to our country for leadership, now worry about what is next.

I ask the five of you to combine your wisdom, your courage and your patriotism. You can speak out together against current abuses and reaffirm constitutional values. You can lead the nation to explore informal and formal next steps.

For the sake of the United States of America and our values, we need your voices now.