With Flynn's guilty plea, is it Trump impeachment time yet? The Founders would be concerned if Trump won with help from a foreign nation on unfriendly terms with the U.S. But we don't have the facts yet.

Cass R. Sunstein | Opinion contributor

Show Caption Hide Caption The fall of Michael Flynn: A timeline Here are the important dates detailing Michael Flynn's relationship with Russia that led to his resignation.

Talk of impeaching President Trump surged after Michael Flynn, his former national security adviser and transition aide, pleaded guilty to lying to the FBI. But what is the real meaning of the Constitution’s mysterious provision authorizing removal of the president and other federal officials for “treason, bribery, or other high crimes and misdemeanors”? Is the growing interest in impeachment simply wishful thinking by Trump's political opponents?

Before we get to current events, let’s insist on a principle of political neutrality.

More: Trump impeachment: House must act now to keep our Republic

More: Robert Mueller terrifies President Trump. Of course he wants him gone.

Under the Constitution, presidents have four-year terms. It’s not legitimate to call for impeachment simply because you abhor the president or think that he is making terrible blunders.

If you are inclined to think that he has committed an impeachable act, you should immediately ask yourself: Would I also think that if I voted for him and thought he was doing a terrific job?

And if you are inclined to dismiss a suggestion that a president might be impeachable, you should immediately ask yourself: Would I also think that if I voted against him and thought that he was doing miserable job?

The Constitution was designed to reduce the risk that impeachment would be a partisan affair. “High crimes and misdemeanors” are a reference to what Virginia’s George Mason called “great and dangerous offenses” — egregious abuses of presidential authority.

Adopted against the background of the American Revolution, the impeachment clause was meant to ensure that We the People would ultimately be in charge. The clause gives us a sword and a shield whenever the president engages in actions that turn out to be treasonous, corrupt or in defiance of the defining national commitment to self-government.

That means that some violations of the criminal law are not impeachable. If a president shoplifts, punches one of his Cabinet members, jaywalks, or cheats on his taxes, he has not committed a high crime and misdemeanor.

At the same time, a president may be impeached for actions that do not violate the criminal law. In The Federalist Papers, Alexander Hamilton carefully explained that the “subjects” of impeachment involve “the abuse or violation of some public trust” — not necessarily crimes.

In the Virginia Ratifying Convention, James Madison specified that abuses of the pardon power would be impeachable, even though they would not violate the criminal law. In Massachusetts, defenders of the proposed Constitution saw impeachment as a way to safeguard freedom, insisting that “no office, however exalted, can protect the miscreant, who dares invade the liberties of his country.”

With respect to current controversies, the most relevant words come from the Constitutional Convention itself. Some of the delegates opposed impeachment, arguing that a four-year term would be short enough, and that if the president were impeachable, the whole system of separation of powers would be at risk.

George Mason offered the decisive answer. He began with these words: “No point is of more importance than that the right of impeachment shall be continued. Shall any man be above justice?”

Then he asked a rhetorical question: “Shall the man who has practiced corruption and by that means procured his appointment in the first instance, be suffered to escape punishment, by repeating his guilt?”

Mason was focusing here on efforts to bribe the electors in the Electoral College. But his argument might well apply to efforts to procure the presidency with the help of officials in a foreign nation, especially one with whom the United States is on unfriendly terms. In view of the founding generation’s acute sensitivity to the risk that national officials might be disloyal to our country, any such efforts would seem to fall in the core of Mason’s concerns.

All this helps to explain what makes special counsel Robert Mueller’s continuing investigation a matter of national importance — whatever your political commitments.

More: Donald Trump to America: Please impeach me

POLICING THE USA: A look at race, justice, media

To be sure, we have to draw some distinctions. It is hardly inappropriate for a newly elected president and his transition team to have discussions with officials in other nations, including Russia.

It is perfectly legitimate for them to explore issues of policy and potential plans. If members of a transition team reach out to other countries, and offer signals about the inclinations of the incoming president, it would be much worse than reckless to start talking about impeachment.

Nonetheless, some lines cannot be crossed — which means that it is appropriate, even essential, to find out exactly what happened.

For all Americans, the impeachment provision is the Constitution’s perfect reflection of Benjamin Franklin’s never-to-be-forgotten response to the question, back in 1787, about what the document’s authors had given to their country:

“A republic, if you can keep it.”

Cass R. Sunstein, who was President Obama's top adviser on federal regulations, teaches at Harvard Law School and is author of Impeachment: A Citizen’s Guide. Follow him on Twitter: @CassSunstein