This is my third impeachment. This is what I’ve learned.

In 1973, as a student journalist, I stood against the back wall of the ornate Senate Caucus Room and scribbled notes as the Senate Watergate Committee held hearings on the tangled misdeeds of President Nixon.

I listened as John W. Dean, Nixon’s former counsel, said he had warned of “a cancer on the presidency.”

In 1999, as a Times reporter, I stood in the Senate Press Gallery and watched senators solemnly pronounce their verdicts in the impeachment trial of President Clinton, including, on one count, a carefully choreographed 50-50 tie.