Suddenly, impeachment can wait. Speaker Nancy Pelosi said Thursday she’ll delay transmitting the two House-approved articles to the Senate, in an obvious ploy for partisan advantage. For anti-Trump legal scholars Noah Feldman and Laurence Tribe, that has created a Schrödinger’s Cat scenario. They disagree on whether President Trump has been impeached at all.

Mr. Feldman says no: “If the House does not communicate its impeachment to the Senate, it hasn’t actually impeached the president.” Mr. Tribe says an affirmative vote on an article of impeachment is sufficient to impeach—but he also claims it’s proper to leave it at that. By declining to transmit the articles of impeachment, he argued in an op-ed that Mrs. Pelosi evidently found persuasive, the Democrats would get a win-win. Mr. Trump would carry the stigma of impeachment and be denied the opportunity to erase it via acquittal.

Messrs. Feldman and Tribe are both wrong. Mr. Tribe errs in asserting that the House can deny an impeached official a trial. Mr. Feldman errs in denying that the approval of articles of impeachment is sufficient to constitute an impeachment. The Senate need not wait for the articles to be “transmitted.” The Constitution grants the House the “sole power of impeachment,” and the Senate the “sole power to try all impeachments.” Now that the House’s job is done, it is up to the Senate to schedule a trial and make the rules for it.

My view—which I suspect much of the public shares—is that Mr. Trump was impeached by a partisan vote and deserves to be acquitted by a partisan vote. The representatives who impeached him along party lines after devising partisan rules of inquiry have no principled argument against a party-line acquittal.

Mr. Dershowitz is a professor emeritus at Harvard Law School and author of “Guilt by Accusation: The Challenge of Proving Innocence in the Age of #MeToo.”