Is the Senate obligated to hold a trial?

The Constitution clearly envisions that if the House impeaches a federal official, the next step is for the Senate to hold a trial. But there is no obvious enforcement mechanism if Senator Mitch McConnell, Republican of Kentucky and the majority leader, were to simply refuse to convene one — just as he refused to permit a confirmation hearing and vote on Mr. Obama’s nominee, Judge Merrick Garland, to fill a Supreme Court vacancy in 2016.

Still Walter Dellinger, a Duke University law professor and a former acting solicitor general in the Clinton administration, said it is unclear whether it would be Mr. McConnell or Chief Justice John G. Roberts Jr. who wields the authority to convene the Senate for the purpose of considering House-passed articles of impeachment.

Either way, though, he noted that the Republican majority in the Senate could vote to immediately dismiss the case without any consideration of the evidence if it wanted.

To date, Senate Republicans have given no indication that they would break with Mr. Trump, especially in numbers sufficient to remove him from office. In their internal debate about what to do, some Democrats have argued that this political reality means that they should instead focus on trying to beat him in the 2020 election, on the theory that an acquittal in the Senate might backfire by strengthening him politically. Others have argued that impeaching him is a moral necessity to deter future presidents from acting like Mr. Trump, even if Senate Republicans are likely to keep him in office.

In that same Federalist Paper written in 1788, Mr. Hamilton wrote that the inherently political nature of impeachment proceedings would be sure to polarize the country.

Their prosecution, he wrote, “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.”