The founders need to be consulted here, though it takes some effort to tease out their reasons for injecting the chief justice into the Senate trial. Out of concern that publicity could undermine free and full debates, the proceedings of Constitutional Convention of 1787 were held in private. We have James Madison’s notes and the recollections of other participants as to what transpired. But, on the whole, we know little about the full deliberations, as there are gaping holes in Madison’s notes. As a result, one of the primary sources most scholars and lawyers consult to understand the founders’ intent is the Federalist Papers—published anonymously at the time but, as we now know, written largely by Alexander Hamilton, who managed to marshal arguments in favor of the Constitution’s various provisions more or less as they emerged in final form from the convention in Philadelphia.

Federalist 65 is the most important paper for understanding the role intended for the chief justice in an impeachment trial. Writing in the spring of 1788 to “the People of the State of New York,” Hamilton laid out the considerations that went into making the Senate the body to try impeachments, and, in a couple of very important sentences, he explained why the chief justice would preside over the trial.

Federalist 65 begins with a debate about the composition of what Hamilton consistently called the “court of impeachments.” We know that the House of Representatives was to have the “sole power” to impeach or accuse. Note that there is no provision for any other branch of the government to take part in the House’s impeachment inquiry; the founders did not insert, for example, a member of the Supreme Court or an officer from the executive branch. That is not true with impeachment trials; the founders intentionally inserted a representative of the judicial branch, namely, the chief justice, into a process taking place in the legislative branch—a not insignificant imposition. This is the first clue that the chief justice was meant to play a substantive, not just ceremonial, role in the “court of impeachments.”

Secondly, when it came to the composition of the impeachment court, the founders considered various alternatives to the Senate. They started with the idea to use the Supreme Court in full, but that was rejected. Another popular proposal was to have the Senate and the Supreme Court (both smaller in number at the time) sit together as one body when trying impeachments. This sort of conglomeration was the model followed by the state of New York at the time, Hamilton noted in Federalist 66.

The arguments Hamilton made against having the Supreme Court act as the impeachment court were three-fold: 1) the members of the tribunal were not seen as “endowed with so eminent a portion of fortitude” as the senators; 2) it was doubted whether the justices “would possess the degree credit and authority” among the people as would elected representatives; and 3) the court was expected to be too small in number to make the profound decision of impeachment.