The search for presidential parallels can be instructive and thought-provoking, even when considering the unparalleled presidency of Donald J. Trump. Trump sees himself as the second coming of President Andrew Jackson — minus, one supposes, the battle wounds, the duels and the undying devotion to a single wife, even after her death.

Still, the Trump-Jackson parallel is plausible. Each appalled the Washington establishment, relished wielding executive power and exhibited a notoriously thin skin while plowing ahead with his agenda and making enemies with ease.

But a more telling parallel might be Trump and another “Jacksonian” president. That would be the other Scots-Irish Tennessee president — the nearly forgotten, but highly consequential one-term “dark horse” Democratic president, James Knox Polk of Mexican War fame and infamy. It was a war historians have generally labeled a land grab, even a crime.

As his party’s candidate in 1844, Polk spelled out precisely what he hoped to accomplish as president. President Polk then proceeded to do exactly what he said he was going to do. (Sound familiar?)

Well, almost exactly. Polk had campaigned for the “re-annexation of Texas and the re-occupation of Oregon.” But the Republic of Texas came into the union just before Polk’s inauguration by way of a congressional resolution. And the Oregon border question was settled short of war with England and well short of “fifty-four forty or fight” — a reference to the line of latitude American expansionists thought suitable.

Polk also sought to add California to the national trophy case — by purchase if possible, by war if necessary.

That extraordinary prize was won in the Mexican War, yet it is a conflict that has gone largely uncelebrated and even unmentioned ever since. After all, it was a war promoted and fought mainly by those who were determined to spread slavery westward and perhaps even southward as well.

Polk himself was not terribly interested in slavery one way or the other. He wanted territory, and especially had his eye on the ports of San Diego, San Francisco and Seattle. During his only term in office he obtained all three, thereby setting the stage for America to become a Pacific power, as well as for his own exit from the political stage. Why bother running for re-election when he had already accomplished his goals?

In his magisterial “The Year of Decision 1846,” the great liberal historian Bernard De Voto tells us that Polk’s mind was “rigid, narrow, obstinate, far from first rate … ” More than that, the man himself was “pompous, suspicious, secretive; he had no humor; he could be vindictive; and he saw spooks and villains.”

Does any of this remind anyone of another president?

Lest there be any lingering doubts, De Voto completes his word portrait of our 11th president with this: “But if his mind was narrow, it was also powerful and he had guts … his integrity was absolute and he could not be scared, manipulated, or brought to heel. No one bluffed him, no one moved him with direct or oblique pressure.”

Does this capture a subsequent president whom we think we know? OK, the integrity thing might be questioned, but not if we’re thinking about Trump’s policy objectives. There were no Trumpian promises about being able to keep your favorite undocumented laborer, if you like him.

All of this points not simply to a presidential parallel, but to historical ironies and philosophical questions.

President Polk’s war led to the creation of a “free soil” movement, which in 1856 produced the Republican party, whose first platform called for the containment of slavery. Four years later the country elected as president Abraham Lincoln, who as a congressman had opposed Polk’s war. Lincoln’s commitment to “free soil” and the “ultimate extinction” of slavery provoked the secessionist crisis that led to the Civil War and slavery’s rather rapid demise.

There is some talk today of a second civil war. Is a Trump presidency, like Polk’s presidency, a prelude to such a terrible conflict? If so, might it be triggered by a secessionist movement in the American southwest? Some Californians on the left are hinting at such. So are some Texans on the right.

This leads to a second irony and more questions. If Polk can be credited with adding a huge swath of territory to the American empire, might Trump one day be credited with preserving that long-ago victory by reversing the gradual makeover of the southwestern United States?

Will Trump secure his border wall, and will that wall secure the American border? If so, will the result stir or calm secessionist waters?

Will Polk’s criminal war be matched by Trump’s “immoral” wall(to borrow from House Speaker Nancy Pelosi)? If so, will a beneficent empire be reinvigorated? Or will it be broken?

A beneficent American empire? Historian/geographer Robert Kaplan, in “Earning the Rockies,” correctly regards the United States as at once a nation, an empire and a continent, thanks in no small measure to the “rigid, narrow and obstinate” Mr. Polk. Kaplan also contends that America became a great power in the 20th century in part because of Polk’s unwillingess to be bluffed, manipulated or brought to heel.

Whether or not the United States remains a great power in the 21st century may well depend on the actions of another president who cannot be bluffed, manipulated or brought to heel. All of which brings us to a moral question, even a moral dilemma.

Can bad deeds lead to good and even great outcomes? Was the Mexican War a bad deed and yet a good deed? Is a border wall a bad deed or a good deed — or both?

Kaplan calls the Mexican War a “crime.” And yet he is convinced that the fruits of that war helped make America a great power and a great force for good in the 20th century, as when it came time for the United States to fight World War II and prosecute the Cold War.

Will the United States remain united and a force for great good in the 21st century? If so, will it be because President Trump has taken steps to secure President Polk’s victory — and in a way that will make another Lincoln unnecessary?

Or will Trump, like Polk, set in motion forces that will one day tear the country apart? Only time will tell.


John C. “Chuck” Chalberg writes from Bloomington.