The big lie behind the impeachment of President Trump is the notion that the Democrats are better custodians of our national security than the Republicans. It has animated the long campaign to sabotage Mr. Trump’s presidency — right up to the the eve of the verdict in the Senate, when Speaker Pelosi, at a press conference, likened herself to Paul Revere, but crying, “the Russians are coming, the Russians are coming.”

“The day we were bringing the articles to the floor,” Mrs. Pelosi reminded the press, “I quoted the ‘Midnight Ride of Paul Revere.’” That’s the Henry Wadsworth Longfellow classic in which the Boston silversmith rides through the night to warn his countrymen that the British are coming. “In this case,” Mrs. Pelosi said, “the Russians are coming, the Russians are coming. The President has led a clear path for them to interfere.”

You have to pinch yourself to remember that the Speaker was speaking about an impeachment in which Mr. Trump was accused of inviting Russia’s foe, Ukraine, to interfere in our election. And to do so by investigating possible corruption in the family of Vice President Biden, one of the arch-doves in our politics. Plus, too, it was the Democratic administration, not Mr. Trump’s, that refused to arm Russia’s foe.

If Mrs. Pelosi seemed confused at the moment of truth in the impeachment, it’s not surprising. The falsehood she was seeking to advance goes all the way back to Vietnam, off to which war America went on a Democratic president’s vow that we would pay any price, bear any burden to assure the success of liberty. In the face of, in Vietnam, a relentless, years-long attack by the Soviets, it was the Democrats who beat a retreat.

Mrs. Pelosi herself is a tribune of what President Reagan’s envoy to the United Nations, Jeane Kirkpatrick, called the “San Francisco Democrats.” In our view, this is why, despite all the constitutional points on which the Democrats prosecuted the President, the whole thing failed to compute. It’s why they failed in the House to gain a single Republican vote for impeachment and why they lost on an almost straight party line in the Senate.

It’s a sad and ironical moment for the Democrats. They have long since shed the mantle of internationalist foreign policy. They abandoned it when it came time to deploy the cruise and Pershing missiles against the Soviet. They abandoned it when it came time to choose between Free China and Red China. They lost it in the maneuvering against the Soviet in, say, Honduras. It was President Obama who met with President Raúl Castro.

We understand the GOP is changing, as well. Mr. Trump calls Iraq a horrible mistake, but it’s hard for the Democrats to score him on that because . . . well, they agree with him (the Sun doesn’t; it was, in our view, the retreat that was the mistake). Mr. Trump is rethinking the North Atlantic Alliance (albeit mainly to win from the Europeans their agreed-upon funding). It’s the Republicans who are rebuilding our military.

All this is a context in which Mrs. Pelosi’s quest to impeach the President looks absurd. Or worse. Her rewrite of Paul Revere’s midnight ride to “the Russians are coming, the Russians are coming” smacks of the very McCarthyite tactics her party once abjured. It didn’t work. The Republican-led Senate stood firm and may well — we don’t want to wax overly-optimistic here — have ended the era of political impeachments.