They (courts of impeachment) are of a nature which may with peculiar propriety be denominated POLITICAL, as they relate chiefly to injuries done immediately to the society itself. The prosecution of them, for this reason, will seldom fail to agitate the passions of the whole community, and to divide it into parties more or less friendly or inimical to the accused. In many cases it will connect itself with the pre-existing factions, and will enlist all their animosities, partialities, influence, and interest on one side or on the other; and in such cases there will always be the greatest danger that the decision will be regulated more by the comparative strength of parties, than by the real demonstrations of innocence or guilt.
Hamilton, Alexander. The Federalist Papers.
Two things. First, Congressional impeachments happen because a “public man” engaged in “the administration of public affairs”—is accused of violating the public trust. Nothing more, nothing less.
Second, we might say that Hamilton had a fantastic crystal ball—or, that he was expressing what was then and is now, common sense. For the Senate, “resting entirely on the basis of elections,” will be “too often the leaders or the tools of the most cunning or the most numerous faction, and on this account, can hardly be expected to possess the requisite neutrality towards those whose conduct may be the subject of scrutiny.” Common sense.
But in the end, Hamilton chooses optimism, asserting “where else than in the Senate could have been found a tribunal sufficiently dignified, or sufficiently independent? What other body would be likely to feel CONFIDENCE ENOUGH IN ITS OWN SITUATION, to preserve, unawed and uninfluenced, the necessary impartiality between an INDIVIDUAL accused, and the REPRESENTATIVES OF THE PEOPLE, HIS ACCUSERS?” Optimistic. Just like us.
And he would be disappointed. Just like us.