"The President ... shall be removed from Office on Impeachment for, and Conviction of, Treason, Bribery, or other high Crimes and Misdemeanors." So reads Article II, Section 4 of our Constitution. President Donald Trump is charged with "abuse of office" and "obstruction of Congress," crimes that professor Alan Dershowitz, a member of his legal team, has called too vague to be a charge equal to treason or bribery.

In the context of the Civil War-era impeachment of President Andrew Johnson, Justice Benjamin Robbins Curtis argued for the necessity of a crime proven beyond a reasonable doubt. There are difficulties with crediting this view. It has been settled by the great weight of authority that conviction of a crime is not a predicate to impeachment. Impeachment is concerned with treachery, the use of presidential power that betrays the Constitution or that elevates the personal interests of the president over those of the nation.

Impeachment, as Dershowitz explained, does not depend upon the showing of a "technical" violation of a criminal statute. Thus, a president who engaged in criminal behavior, but who could not be prosecuted because the statute of limitations expired, still could be impeached.

The twists and turns of Dershowitz's argument are challenging to follow, and the absolute clarity he sees is unfortunately not shared by all, or even many. What is understood is that the Constitution envisages impeachment to serve an important function different from the criminal laws. Criminal prosecution is to punish, to deter, to rehabilitate; impeachment safeguards the republican and democratic structure of the Constitution itself.

This distinction is all over the document - including that which precludes indicting a sitting president. Indicting the chief executive would effectively eliminate a president's capability to faithfully execute the law. Besides distracting him with his own defense, indictment makes a sitting president the countersign of what it means to be our chief law enforcement officer.

And then there is the standard of proof. Dershowitz assumes it to be "beyond a reasonable doubt," but that is unsettled. This most demanding standard applies when loss of liberty is in the balance. But conviction by impeachment will not "lock him up." Perhaps Trump's imprisonment might result, post-removal, but only after the ship of state has been anchored in the hopefully capable hands of s successor.

So what is the factual claim against President Trump? It is just this: The president has subordinated the national interest to his own, or even worse that he has given aid and comfort to a foreign adversary. Facts are facts, or at least they are supposed to be a matter of reality incapable of being manipulated to mean something they are not. Alas, people do see things differently because of context (known to some but not others) or because of capability and experience (a trained doctor identifies illness that would escape others without medical study).

It is enlightening to be sensitive to how we see differently unless the difference is solely attributable to partisan bias alone. Can the Senate jurors keep partisanship at bay? Can we?

Here, there is much to digest. Was it wrongful for the president to slow the payment of taxpayer money to Ukraine, a country that was rife with corruption? Did a portion of that corruption include payment of hundreds of thousands of dollars or more to the son of a powerful father? In all the hours of presentation, there has been little or no inquiry as to whether the payments to Hunter Biden by Ukraine energy firm Burisma Holdings were implicit inducements to then-Vice President Joe Biden. We need to hear from both Bidens; they deserve a chance to clear the family name.

Rep. Adam Schiff (D-Calif.) makes the opposite case that the president unlawfully impounded a portion of the funding Congress authorized for Ukraine to gain political advantage. Others speculated that the president was doing a favor for Russia's Vladimir Putin, whom Trump has found reason to praise. Intelligence sources identify Russia as the source of the false narrative blaming Ukraine for disrupting the 2016 election. Putin has expressed his delight that the media bought into his lie. It troubles Americans greatly to even contemplate our president - knowingly or unwittingly - doing Russia's bidding.

Another of the president's lawyers, Kenneth Starr, thinks this is the "age of impeachment." He is right, even as he overlooks that he was a prime mover of the unfortunate criminalization of the separation of powers. The Starr Report likened Bill Clinton's sad marital infidelity into a basis for impeachment. It wasn't, but the lowering of the impeachment standard occurred in the 1990s, not just now.

Is this impeachment, then, repeating the Starr mistake? Maybe, but a special counsel of impeccable credentials, Robert Mueller, did not fully exonerate the president given the panoply of specific criminal prohibitions of foreign support or interference in our national elections. Mueller did not think it his place to prosecute the president without trial, but the Mueller Report (scarcely mentioned in the present proceeding) details statutory and case support for such prosecution.

In all of this, little has been said of the other dark shadow over the president - the nagging suspicion that he and a wealthy few are making public decisions based on private self-interest. Every other senior government official must disclose actual or likely economic conflicts and take steps to recuse or resolve them before entering office. Congress may or may not choose to convict and remove Trump, but it has no reason not to write into law that every candidate for the presidency in 2020 and thereafter must make fulsome financial disclosure as a pre-condition of running.

The impeachment proceeding is not an embarrassment. The arguments on both sides have been made well and they demonstrate that the recent global isolationism leaves unaltered America's founding commitment to the rule of law in a democratic republic. Arguments, of course, are only words, and it remains to be seen whether the members of the Senate will affirm this founding commitment in their actions as they deliberate.

In the "age of impeachment," there is a tendency for "We, the people" not to reason but to intimidate and threaten with political retribution. Is there a way to mitigate this party-induced bias? Yes, the secret ballot. The Constitution provides that the "Senate [has] the sole power to try all impeachments," and absent a fundamental denial of due process, the rules chosen are beyond judicial review.

Secret ballots are traceable to ancient Greece and, in times of great division in history, the practice has freed the exercise of conscience. Some nations guarantee ballot secrecy; the U.S. Constitution allows for it where fair judgment requires. All it takes is 51 Senate votes, and some members of Congress speculate that even a one-vote majority would invite up to 35 Senate jurors to be a "profile in courage," whichever side - in light of all the relevant facts and the law - proves the most worthy.

Douglas Kmiec is professor emeritus of constitutional law at Pepperdine University School of Law. He served as the U.S. ambassador to Malta from 2009 to 2011, and headed the Office of Legal Counsel during the Reagan and George H.W. Bush administrations.