Yet Mr. Trump’s defiance can, in and of itself, form the basis for an additional impeachment article — a fact that Nancy Pelosi, the speaker of the House, recognized on Thursday. “Ignoring subpoenas of Congress, not honoring subpoenas of Congress — that was Article III of the Nixon impeachment,” she said.

President Trump’s assertion that there is nothing left to learn from congressional hearings — which, unlike the Mueller investigation, would be televised — may be correct. But that is beside the point; it is up to Congress, not him, to decide.

He also clearly fears the dramatic spectacle that such hearings would surely provide. Once again the Nixon model applies. Who can forget the scenes of John Dean, Nixon’s former White House counsel, testifying about the “cancer on the presidency” and hush money payments to the Watergate burglars?

Nor can students of Watergate forget the power of the televised hearings of the House Judiciary Committee during the summer of 1974. Far from being politically divisive, they proved a dignified and appropriate response to egregious presidential misconduct — enough to persuade seven out of the committee’s 17 Republicans to vote in favor of at least one of the articles of impeachment (Lawrence Hogan of Maryland, the father of the current governor of Maryland, was the only Republican to vote for all three impeachment articles).

If the present moment has yet to offer any similar profiles in courage, that does not mean we will never see dramatic conversions. This early in our current process, it is a mistake to presume that no Republican lawmaker, House or Senate, will ever have a crisis of conscience and vote against Mr. Trump. And it is even a bigger mistake to let that presumption influence whether an impeachment process should be initiated or not.

If nothing else, televised hearings would demonstrate that Mr. Trump not only lacks respect for the rule of law, but for Congress and the separation of powers — a fact that, in and of itself, is an impeachable offense.

James Reston Jr. is the author, among other books, of “The Conviction of Richard Nixon: The Untold Story of the Frost/Nixon Interviews.” He advised the British television host David Frost on his interviews with Mr. Nixon in 1977.

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