(CNN video)

There is a shorthand people around politics use when measuring potential presidents: Is this candidate really a “heavyweight” — meaning an individual of seriousness, intelligence and gravity — or is he, heaven forfend, a “lightweight” so unreflective and superficial that he could tap-dance on a soufflé? By every measurable standard, Mario Cuomo, the former three-time governor of New York who died on New Year’s Day at 82, was a genuine heavyweight.

The late Jack Germond, one of the nation’s great political reporters, told a revealing incident from 1977, when Cuomo was running, unsuccessfully, for mayor of New York. Cuomo was holding a news conference on changes needed to reform the abuses in ambulance services in the city. After handing out a fact sheet on the subject, Cuomo answered questions from reporters for 20 minutes before the TV crews began packing up to leave and the reporters put away their notebooks.

But as Germond wrote, “one young radio reporter, a student from Columbia, asked if she could pose a few more questions. Cuomo agreed and then realized from the questions that this young woman had studied the ambulance service problem and probably knew more about it than he did.” What did Cuomo do? He sat there for 45 minutes answering questions, all the time learning. No sound bites on the evening news, just an intellectually curious and honest public man willing to go way beyond talking points. A heavyweight.

Oliver Wendell Holmes once said of another New York governor, Franklin D. Roosevelt, who would become America’s greatest 20th-century president, that he possessed “a second-rate intellect but a first-rate temperament.”

Mario Cuomo — the son of parents who were both Italian immigrants — who did not himself learn to speak English until he began public school in Queens and who would become for an entire generation of Democrats their party’s poetic, public voice, possessed a first-rate intellect.

In the three presidential elections of the 1980s, when losing Democratic nominees carried a total of just 17 states, Cuomo reminded Democrats and Americans of what in fact they had stood successfully for.

Who could forget that eloquence? His fundamental premise about what a proper government should be: “the idea of family, mutuality, the sharing of benefits and burdens for the good of all, feeling one another’s pain, sharing one another’s blessings.”

That was in the speech that made him famous, his keynote to the 1984 Democratic National Convention in San Francisco, in which he taught that “while survival of the fittest may be a good working description of the process of evolution, a government of humans should elevate itself to a higher order” and that “we would rather have laws written by the patron of this great city, the man called ‘the world’s most sincere Democrat’ — St. Francis of Assisi — than laws written by Darwin.”

In an era of chronic Democratic self-doubt, Cuomo remained the principled liberal who dared — when public opinion endorsed capital punishment by a 2-to-1 ratio — to veto seven times bills to reimpose the death penalty.

Unlike his predecessors in Albany — including Nelson Rockefeller, FDR, Averell Harriman, Al Smith and Thomas E. Dewey — Cuomo chose, when he was the clear front-runner for the Democratic nomination, not to seek the presidency.

Vicious, baseless rumors that this proud Italian-American might have some damaging “connection” were contradicted by the vast sums spent by Republicans in negative research against him, which never came up with anything. It was garbage. The question we should ask is not why someone does not run but rather why somebody does run.

Because he was a genuine heavyweight, candidate Mario Cuomo would have commanded the nation’s attention and, perhaps, changed the nation’s direction. But he should be remembered as a serious and significant leader who reminded us well and passionately of what we all owe to one another and to our country.

Mark Shields is one of the most widely recognized political commentators in the United States. The former Washington Post editorial columnist appears regularly on CNN, on public television and on radio. Click here to contact him, or click here to read previous columns. The opinions expressed are his own.