It has taken less than three weeks of the Donald Trump presidency to establish the “A Democrat Did It First” principle of aggressive right-wing defense. For no matter what Trump does amid his dizzying daily assaults on White House decorum, there will always be claims — no matter how ludicrous — of a Democratic presidential precedent.

So when the president targeted Nordstrom for the unforgivable sin of not continuing to stock Ivanka Trump goods, it suddenly became time to blame Harry Truman. To Rush Limbaugh and company, Trump’s use of a White House Twitter account to excoriate a department store chain was the equivalent of Truman threatening a music critic over a scathing review of his daughter Margaret.

Such is what passes for truth in Talking Points America.

Margaret Truman Daniel fancied herself a coloratura soprano. The debut performance of the president’s daughter with the Detroit Symphony was broadcast nationally on radio, an honor not normally awarded to fledgling concert performers. Armed with a pleasant voice but not nearly enough classical training, Margaret was inevitably headed for a rendezvous with reality.

It came in the form of a review by Washington Post critic Paul Hume after Margaret gave a concert in 1950 to a full house at Washington’s Constitution Hall. Hume came right to the point, “Miss Truman cannot sing very well. She was flat a good deal of the time.” And the review went downhill from there.

The 66-year-old president dashed off an intemperate 150-word letter to Hume suggesting that if they ever met, “you’ll need a new nose, a lot of beefsteak for black eyes, and perhaps a supporter below!” But as David McCullough stresses in his Pulitzer Prize-winning Truman biography, the president was reeling from the sudden death of his friend and press secretary Charlie Ross. Had Ross been alive, the letter almost certainly would never have been mailed.

The differences with Trump’s tweets begin with the detail that Truman’s attack on Hume was never designed to become public. Rather than running in the Post, a leaked copy appeared on the front page of the tabloid Washington News. Moreover, Truman never threatened Hume’s career, the Post’s profits or anything bigger than the music critic’s nose.

White House Sale

Trump’s press secretary Sean Spicer claimed that the president’s message “was less about his family business and [more] an attack on his daughter.” But any ambiguity about the intent of the tweets was erased Thursday morning when top Trump strategist Kellyanne Conway advised Fox News viewers, “Go buy Ivanka’s stuff I would say. … I’m going to give a free commercial here: Go buy it today everybody, you’ll find it online.”

You don’t have to be a legal expert to sense that there might be something tawdry in a presidential aide hawking a commercial brand from the White House briefing room. It also appears that Conway’s “free commercial” violated federal ethics rules that bar using “public office … for the endorsement of any product.”

In a sense, you have to feel sorry for President Trump. He embodies Oscar Wilde’s dictum that a cynic “knows the price of everything and the value of nothing.”

In Trump’s apparently stunted inner life, the only things outside his family that matter are business deals and profits. Take them away — and Trump is left with his face on the television screen, the distant roar of exaggerated crowds and the uncomfortable obligation to take phone calls from world leaders.

No president offers a greater contrast to Trump than that noted critic of music critics, Harry Truman. This failed Kansas City haberdasher was animated by the now sadly quaint belief that the presidency should not be treated as a road to riches.

Personal integrity

When Truman left the White House on Jan. 20, 1953, he was broke in a way that Hillary Clinton (let alone Trump) could never understand. As McCullough writes in his biography, “[Truman] had come home without salary or pension. He had no income or support from the federal government other than his Army pension of $112.56 a month.” In fact, in his last weeks as president, Truman had to take out a bank loan to carry him and his wife Bess financially.

But even in private life, Truman was determined not to exploit the presidency. He turned down numerous no-show jobs paying the equivalent of more than $1 million a year. In contrast, Bill Clinton would have asked only two questions: “Where do I sign? And can I also get a contribution to the Clinton Foundation?”

Maybe it is naive to romanticize Harry Truman, a man who was born in the 19th century, just 19 years after the end of the Civil War. But I can’t help believing that something good about America — reflected in Truman’s rock-ribbed personal integrity — has become lost along the greed-locked streets of 21st century Washington.

Roll Call columnist Walter Shapiro is a veteran of Politics Daily, USA Today, Time, Newsweek and the Washington Post. His book on his con-man great-uncle was just published: “Hustling Hitler: The Jewish Vaudevillian Who Fooled the Fuhrer.” Follow him on Twitter @MrWalterShapiro.