President Donald Trump has a painting of Andrew Jackson in the Oval Office, but as he tries to browbeat Denmark into coughing up Greenland, maybe he should add a portrait of a Jackson acolyte — James K. Polk. 

If cold-eyed American expansionism is the theme, there are few better representatives than the 11th president.

He added more than 1 million square miles to US territory and extended the country all the way to the Pacific, making him the most successful president not celebrated as part of the American pantheon.

Trump’s impulse to throw his weight around and assume control of sparsely populated, strategically desirable territory recalls Polk.

A thoroughgoing Jacksonian populist, he unexpectedly won the Democratic nomination for president in 1844 (much of what I relate here, by the way, is drawn from my book “The Case for Nationalism”).

He ran on a platform urging what Democrats called the “re-annexation” of Texas and the “re-occupation” of Oregon.

Texas was a flash point: Anglos settled there when it was a province of Mexico, rebelled against the........

© New York Post