The president of the United States is on trial in the Senate. It is an impeachment trial and, thus far, has consisted of remarks made by impeachment managers from the House of Representatives, who have argued that the president should be removed from office for abuse of power and contempt of Congress, and the president's lawyers, who have argued that he did not abuse power or behave contemptuously, and even if he did, those are not impeachable offenses.

These arguments often rely on differing views of the relationship between the three branches of the federal government. That relationship is called the separation of powers.

The separation of powers reflects that the three branches are constitutionally equal, have separate duties and that no branch can lawfully perform the duties of the other two. Congress writes the laws. The president enforces the laws. The judiciary decides what the Constitution and the laws mean.

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When the Constitutional Convention took place in Philadelphia in 1787, its ostensible purpose was not to create a new government but to amend the old one. The old one was the Articles of Confederation, which enabled the 13 states to retain their autonomy and created a central government that was subservient to the states.

James Madison was the driving force behind the convention, and recent scholarship removes some of his halo by revealing his duplicity.

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Stated differently, though the public faces pushing for the convention claimed its purpose was to amend the articles, Madison and his colleagues plotted their real purpose for months -- to craft and offer a new constitution.

Madison believed that only a strong central government could pay the Revolutionary War debts, diminish the ruinous commercial rivalries among the states that had produced monopolies and tariffs, and be a presence on the world stage.

The debates at Philadelphia are rich and revealing. Alexander Hamilton wanted a parliamentary monarchy, with a king and Congress strong enough to regulate commercial activities. George Mason wanted the states to remain supreme so Americans, by voting with their feet, could have a continuous menu of governments from which to choose.

Madison's political sagacity produced the separation of powers. Madison believed that by dividing the core functions and powers of government, his scheme would preserve personal liberty. He and his colleagues had just rejected a monarchy that put all the power in the hands of the king and a subservient Parliament. That system was not designed to preserve personal liberty.

But the separation of powers was. It produced tension and even jealousy among the branches, and the constitutional interplay among them prevented one from dominating the other two at the price of personal freedoms. The federal government simply would not work without each branch respecting the others. And any two branches could prevent the third from usurping power. That theory animated Madison and his colleagues.

Yet, there is built into the system not only equality but also primacy and exclusivity. While the branches are equal under the Constitution, they each possess areas of governance immune from interference by the other two. For example, only Congress can appropriate funds from the federal treasury. Only the president can command the military. Only the courts can invalidate laws or restrain constitutional violations.

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Today, it is jurisprudential and constitutional dogma that each branch has powers unique to it and thus immune from interference by either of the other two.

Now, back to the legal arguments in the president's Senate trial. Ordinarily, when Congress wants to acquire documents from the president, there is a constitutional tug of war between them. And often that dispute is resolved by the courts. However, the courts can have no say if the dispute happens when one branch is exercising duties immune from interference by the other two. Thus, no court can tell the president to deploy troops or Congress to raise or lower taxes.

In the case of impeachment of the president, the Constitution gives "sole power" to the House of Representatives. In the case of an impeachment trial, the Constitution gives exclusivity to the Senate. There is no place for presidential resistance or judicial interference, so long as the House and Senate arguably follow the Constitution.

In President Trump's case, the House has. It has not charged him with having bad hair. It has charged him with high crimes and misdemeanors by coercing a foreign government to aid his reelection campaign, a crime; and by refusing to perform a required governmental duty until the foreign government gave him a personal benefit, a crime; and by refusing to comply with congressional impeachment subpoenas, a crime.

The president's lawyers have misrepresented the separation of powers by arguing that when Congress and the president are at loggerheads over congressional demands for documents or testimony, it becomes the duty of the Congress to turn to the courts. That is a general proposition of law, yet an incomplete one, as it does not apply in cases of presidential impeachment where the House has more than primacy -- it alone has power.

Stated differently, the president has no legal or constitutional basis to reject House subpoenas when the House is conducting an impeachment inquiry. And the House has no need to seek the imprimatur of the courts to address presidential resistance. The historical remedy for such presidential resistance is impeachment. We know this from the Nixon and Clinton impeachment investigations.

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We also know from those experiences that if the Senate is faithful to the Constitution, then Trump's trial will be a search for the truth. And those offering to tell the truth should be welcomed, not pilloried.

How can the Senate be faithful to the Constitution if it suppresses the truth?

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