“It all started with the border, and that’s still where it is today.” These are the first lines of the Drive-By Truckers’ song “Ramón Casiano,” released just before the election of Donald Trump in 2016. I’ve been humming the song for much of the last four years, because Mr. Trump’s journey to the White House began with promises of a “great wall” along the border, and that’s also where it ended.

The song describes a 15-year-old Mexican boy shot and killed by Harlon Carter, who was 17, in Laredo, Texas, in 1931. Mr. Carter later led the Border Patrol and then the National Rifle Association, overseeing its transition from an organization for sportsmen and hunters to one focused on Second Amendment rights.

Mr. Casiano was killed a couple hours away from McAllen, Texas, in the Rio Grande Valley, where Mr. Trump went just a few days after delivering a fiery speech that spurred violence at the U.S. Capitol on Jan. 6. It was a swan song for a presidency whose legacy will be, above all else, the divisions he has sown; a coup de grâce after an attempted coup d’état.

Mr. Trump went to Texas to commemorate the completion of mile 45 of his new border wall — a symbolic location for the 45th president of the United States. Despite Democrats’ hopes that Joe Biden would flip the state, Mr. Trump found support among Hispanics along the border, who, he said, understand “better than anybody” that it takes strong law enforcement to “help them live safe lives.”

In his speech, he celebrated his accomplishments, and lobbed grenades at his opponents as his walls of support back in Washington crumbled. The 25th Amendment provision to take away presidential powers was of “zero risk” to him, but it “will come back to haunt Joe Biden and the Biden administration,” he said.

Despite rabid opposition, the border wall looming behind him was a win. With its construction, he had defended the nation, prevented terrorists from entering the country, saved jobs for Americans, arrested and deported hundreds of thousands of criminal migrants, and, as an unintended benefit, stopped infected immigrants from passing the “China virus” to U.S. citizens. He did all this, he said, while also improving relations with El Salvador, Guatemala, Honduras and Mexico.

It is a symptom of our division that he can live in a friction-free zone that doesn’t require him to grapple with contradictory facts. His supporters hear the words of a martyr who defended them to the end so their country can remain safe and free. His opponents hear a jingoistic refrain — the repeating chorus of his presidency — that criminalized hard-working immigrants.