Michael D'Antonio is the author of the book " Never Enough: Donald Trump and the Pursuit of Success " (St. Martin's Press). The opinions expressed in this commentary are his.

(CNN) "I could stand in the middle of Fifth Avenue and shoot somebody and I wouldn't lose voters."

When then-candidate Donald Trump raised his hand to imitate firing a pistol, he couldn't have known that a mass shooting at a Parkland, Florida, high school would turn his bravado into shame. Today his bragging performance -- something no thinking candidate would ever say and do -- is a haunting reminder of his failure as a politician, a president and a human being.

At other moments he stressed that he was so rich that he couldn't be bought by campaign donors, which meant that only he could act on the nation's behalf without yielding to special interest pressure.

Now, in the days after Parkland, when a response -- independent of special interest pressure -- is greatly needed, the President cannot deliver. Were he really the man he promised to be during the campaign, he would have been free to advocate any policy. However, during the campaign, he benefited from help by the NRA to the tune of $31 million — nearly $11.5 million to support Trump and almost $20 million against Hillary Clinton -- and voters who listen to the organization supported him. Thus, when he sat down with grieving survivors of Parkland and other shootings, he was burdened like any other politician who tries to make common cause with ties to a special interest group. With dry eyes, and little apparent emotion, Trump offered the idea of adding more guns to schools, by arming teachers.

Trump won a job that requires some of the virtues he advertised and many more, including the ability to set ego aside to unite a diverse and disparate people. At his first opportunity to do so -- his inaugural speech -- Trump showed he didn't possess this quality as he claimed to be taking office at a time of "American carnage" and appealed only to the loyalists who he thought would let him shoot someone on Fifth Avenue.

With his first serious order, which attempted to close America's borders to people coming from certain Muslim majority countries, Trump showed he would use his special powers -- independence and the strength of his base -- to pursue unpopular ends through means that many, including some federal judges, found questionable.

Time and again, Trump demonstrated that his do-it-my-way ego, and not some special gift for leadership, was driving his presidency.

• Confronted with the fact of Russia's effort to influence our election and degrade our democracy, he has cozied up to Vladimir Putin.

• Challenged by a troubled immigration system that has left many so-called Dreamers in limbo, he created a crisis by moving to end DACA and then failing to craft a real solution.

• Given the opportunity to bring America's infrastructure up to snuff, he hasn't been able to make any real progress.

With every challenge, Trump has had the opportunity to fulfill his promise to be the president he promised to be. Time and again, he either refused or failed to understand the actual power he possessed. In between the ceremonies where he signed documents with a flourish, Trump could have fashioned bipartisan majorities to enact policies most Americans favor. Nowhere is this more true than it is in the area of gun violence.

Repeated polls have found that a majority of Democrats and Republicans supports background checks for every gun purchase, barring people on the no-fly list from purchasing guns, a federal database to track all gun sales and a ban on assault-style rifles.

JUST WATCHED Trump shifts tone at CPAC Replay More Videos ... MUST WATCH Trump shifts tone at CPAC 02:22

The 17 people killed at Parkland were shot by a gunman wielding the overwhelming power of an assault weapon. The same type of firearm was used in recent mass murders in Las Vegas, Sutherland Springs, Texas, Orlando, Florida, and San Bernardino, California. The same weapon was used in the mass shooting at Sandy Hook Elementary School in Connecticut in 2012.

Sandy Hook, where 20 first graders and six adults were killed, was supposed to change everything, but it didn't. Politicians captured by the donations and voting power of the National Rifle Association blocked the kinds of laws most Americans favored and the killings continued.

JUST WATCHED NRA chief addresses Parkland shooting, attacks Dems Replay More Videos ... MUST WATCH NRA chief addresses Parkland shooting, attacks Dems 02:23

The independence Trump claimed was supposed to make it possible for him to use common sense to solve serious problems. He was, as he told me once, "the people's billionaire" and this meant that he had a kind of superpower that would enable him to defend the nation, heal partisan divides, create coalitions, and generally Make America Great Again.

But by forming an alliance with the NRA, President Trump would have to rely on some other qualities to act with the kind of strength he claims to possess. Unfortunately, even he seems to know that he is deficient.

Study the notes written on a card the President held, which a photographer captured, and you see he wanted to remember to at least demonstrate that he cared. At the top of the list was, "What would you want me to know about your experience?" At the bottom is written, "I hear you."

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The empathy Trump's notecard stressed that he practice has come naturally to most presidents. In similar times of crisis, Barack Obama, George W. Bush, Bill Clinton and others have instinctively shared in the grief of victims and been moved to act. The fact that Trump needed a written reminder to show sensitivity, curiosity, kindness, compassion, courage and conviction is a pathetic and ultimately unsettling sign that even after a year he can't quite do his job.