We need to have these kinds of conversations about the election honestly, rationally, and now. The sooner the better, for chaos could lead to a nightmare scenario: the possibility that President Trump might take advantage of the unfolding health crisis to delay the November election.

Alarmist? Not for anyone who’s paid even glancing attention to the president’s will to power and contempt for constitutional convention. Though he’s recently signaled that postponement isn’t an issue, in the past he’s also joked — at least we think he was joking — about blowing past the two-term limit imposed on presidents by the 22nd Amendment. He retweeted Jerry Falwell Jr.’s suggestion that Mr. Trump be given two additional years in office to make up for time lost to the Mueller inquiry. And he has long trafficked in conspiracy theories about unproven voter fraud in 2016.

The good news is that the Constitution so ably defended by Lincoln gives the executive virtually no control over the timing of elections. Anxious about monarchal absolutism, the founders invested Congress, not the president, with the power to schedule the selection of presidential electors. In a 1934 decision, the Supreme Court held that Congress has every “power essential to preserve the department and institutions of the general government from impairment or destruction, whether threatened by force or corruption.” By statute, Congress has set the date — the first Tuesday after the first Monday in November, every four years — and the power to alter that date lies not with the branch established by Article II, the executive, but with the lawmakers whose authority is rooted in Article I.

Scholars do not believe that even action by the president under national-emergency powers could postpone the quadrennial election unless Congress agreed — which means the Democratic House may be the only bulwark against constitutional chaos come fall.

These are early days in this crisis. We could do worse, though, than to look to Lincoln. When he wrote his letter about possible defeat in the summer of 1864, he said he would stay at his post until the last hour, true to his oath, making the best of things with President-elect McClellan to “save the Union between the election and the inauguration; as he will have secured his election on such ground that he cannot possibly save it afterwards.” In the gloom of disunion, a bit of light. May we find our way forward as Lincoln — and all of us — did in other days of darkness.

Jon Meacham is the author, most recently, of “The Hope of Glory: Reflections on the Last Words of Jesus from the Cross.”

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