It’s tempting to call Senator Susan Collins’ announcement of her intention to vote for Judge Kavanaugh a profile in courage — and it surely is that. In recent weeks she has been subjected to threats of violence and what she considers to be a bribery attempt by those who vowed to punish the decision she just announced with $2 million in donations to her campaign opponent.

Yet what strikes us about Senator Collins’ magnificent moment is that it is about more than courage — it is a profile in substance. The Maine Republican is practically the only person in the Senate to approach this decision by reasoning out the substance of the constitutional questions that have the Democrats so panicked. She parsed the parchment’s preambular purpose of a more perfect union.

This didn’t entirely surprise us. For we have twice or thrice encountered the senator in the dining room of one of America’s greatest newspaper publishers, Alan Baker, back when he owned the Ellsworth, Maine, American. Those dinners were off the record, but we don’t think it would violate the ground rules to say we came away from the table with an enormous regard for Ms. Collins’ character.

How that shone through today. The senator touched on Brown v. Board of Education (which ended separate but equal), Griswold v. Connecticut (which found among the shadows and penumbras of the Bill of Rights an entitlement to privacy), as well as Roe v. Wade and Planned Parenthood v. Casey. She spoke of Judge Kavanaugh’s articulation of the logic — and constitutional glue — of precedent.

What riveted us, though, was the senator’s fidelity to fairness. She made this clear from the start, saying the confirmation process had become “dysfunctional . . . a caricature of a gutter-level political campaign.” She proceeded to lace into those who declared against Judge Kavanaugh even before the hearings, including some who declared against him before his name was announced.

Ms. Collins didn’t mention Senator Schumer by name. Her remarks, though, will stand as a sharp rebuke of his leadership of the Democratic caucus. She noted, without naming him, Senator Schumer’s blather about how the confirmation process was not a trial, and then, whammo.

“Certain fundamental legal principles about due process, the presumption of innocence, and fairness do bear on my thinking, and I cannot abandon them,” she confessed in what will become a famous sentence. Added she: “We must always remember that it is when passions are most inflamed that fairness is most in jeopardy.” She called the presumption of innocence particularly relevant “when an accusation departs from a nominee’s otherwise exemplary record.”

The senator treated Judge Kavanaugh’s accuser, Christine Blasey Ford, with respect and care. She believes Ms. Blasey Ford was the victim of an assault. She gave, though, a devastating reprise of the lack of proof against Judge Kavanaugh. She said she was “alarmed and disturbed” by those who suggest that unless the judge is rejected, the Senate condones sexual assault. She welcomed the issue of sexual assault to the van.

Senator Collins’ closure was a call for unity. At one point she spoke of the overlap of the opinions of Judge Kavanaugh and a colleague on the District of Columbia circuit, Judge Merrick Garland, whom, when he was nominated by President Obama, the Senate declined to hear or confirm. Her final hope was for a Supreme Court that issues fewer five-to-four decisions.

The senator ended by announcing her intention to vote tomorrow for Judge Kavanaugh. Senator Manchin quickly followed, ensuring — absent a surprise — that the judge will be confirmed tomorrow, albeit on a narrow vote. There will be time to celebrate that moment when it comes, but it’s not too soon to suggest that Senator Collins’ speech could be a game-changer not only for Judge Kavanaugh but for Senator Collins herself.