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) Bill Clinton could be both Bubba on the front porch and the pastor who bound the nation's wounds after the Oklahoma City bombing. George W. Bush was able to gently declare Islam a religion of peace after the 9/11 terror attacks and, on the eve of war with Iraq, say: "We've got the force necessary to deal with the security situation."

Barack Obama was comfortable rousing partisans with jabs at the GOP at a convention and singing "Amazing Grace" in Charleston, South Carolina.

Think back to FDR and it's easy to recognize that modern presidents have often shown the world different sides depending on the moment, but always in the context of a steady personality.

Then there is Donald Trump, who also has shown two sides, most dramatically in the past 10 days. After giving a measured statement last week condemning hatred and violence in Charlottesville, Virginia, he struck a wildly different tone in an exchange with reporters the next day, drawing widespread condemnation by appearing to equate the far right protesters in that city with those rallying against bigotry.

Then this Monday, he swung back to his earlier tone when, in a speech on his new Afghanistan policy, he condemned hatred and division.

Finally, having apparently strained to act appropriately on Monday, Donald Trump returned from his bad boy timeout Tuesday to address a Phoenix crowd as the familiar, raging and erratic character who appears at his rallies.

He once again bashed the mainstream press and senators in his own party. Then he distorted his record on the racial tragedy in Charlottesville, reminding the world that he lacks the moral core that has allowed previous presidents to display strong personalities while keeping faith with a nation that needs a stable leader.

How is this playing across the country? Not well, according to a new Quinnipiac University poll Wednesday : 62% of respondents said President Trump is doing more to divide the country, and when it comes to the President's response to the violence in Charlottesville, 60% disapprove of his response to Charlottesville compared with 32% who approve.

The fact is, many presidents have been adept at showing different sides to different audiences, but all in the service of a sensible set of goals. Trump's wild tacking from one personality to the other is self-destructive.

The campaign that put Trump in the White House was a manic circus held in a hall of mirrors, and his presidency has brought more of the same. Rather than moderating, he has swung between two poles. On rare occasions he looks and sounds almost presidential as he proposes legislation and meets with diplomats. But more frequently he is the Andrew Dice Clay of chief executives: irresponsible and anxiety-provoking without much regard for the consequences.

If an instrument were devised to measure Trump's mood -- call it a Trumpometer -- it would generally register on the far right-hand side of the scale. This is where "Reckless Trump" muses about the "very fine people" who joined the recent march of the racists in Charlottesville, which culminated in a deadly vehicular attack on anti-hate demonstrators. Heather Heyer died, many more were injured.

On the other side of the meter is "Scripted Trump," who we saw address the country on Monday with a call for healing the wounds he had helped open with his callous response to the events in Virginia.

Scripted Trump appears when the President is persuaded to accept a little discipline -- and a teleprompter. His first State of the Union speech was delivered with the aid of the machine and he got generally positive reviews.

JUST WATCHED Trump's full speech to crowd in Poland Replay More Videos ... MUST WATCH Trump's full speech to crowd in Poland 36:11

He also used a teleprompter for a speech in Poland, where he called on Russia to "join the community of responsible nations," and to "cease its destabilizing activities in Ukraine and elsewhere." Just hours before, however, Reckless Trump refused to accept the national security community's assessment that Russia meddled in the 2016 election, insisting instead that "I think it was probably other people and/or countries."

By denying the facts about Russia's effort to influence the election, Trump neglected his duty to defend American democracy and respect the intelligence services that help safeguard the nation. He did, however, soothe his concern that others might see his election as tainted, and his ego requires this comfort. When Reckless Trump is in the room, it is easy to see that ego is his main concern.

It was Reckless Trump who told Russian Ambassador Sergey Kislyak and Foreign Minister Sergey Lavrov that he had fired FBI Director James Comey, calling him a "nut job." The Trumpometer was also reading "Reckless" when Trump attacked Sen. Mitch McConnell, whom he needs to get legislation passed, and tried to bully Sen. Lisa Murkowski, who helped doom his health care proposal.

Although Reckless Trump often sabotages his own agenda, he causes the greatest damage when he indulges himself on an issue that is vital to both public safety and national unity.

JUST WATCHED Trump: Does the 'alt-left' have any guilt? Replay More Videos ... MUST WATCH Trump: Does the 'alt-left' have any guilt? 01:07

The train wreck of a press conference he conducted at Trump Tower after the Charlottesville tragedy is the most vivid example of this brand of Trump. Irritable and combative -- he often cut others off with "Excuse me!" and complained of "fake news" -- Trump refused to judge the white nationalists on a "moral plane" and repeated his argument that blame for the ugliness should be distributed among both the racists and anti-racists.

The Trump Tower performance was a wild swing away from the more reasonable statement he had made just the day before. It also fit a pattern. When Trump has chosen to moderate himself, to be more like other presidents, he has often snapped back almost immediately to his more combative identity.

For his Monday Afghanistan speech, he pulled himself together for the teleprompter session, which included a reminder that, "loyalty to our nation demands loyalty to one another. Love for America requires love for all of its people."

After all, this is the man who likes to keep people in suspense, wondering which version of him will appear, which has the effect of casting doubt upon every statement. Indeed, as if to prove he's not to be trusted, Trump followed his Monday peacemaking remarks with a trip to Phoenix, where local officials had asked him to stay away because they feared violent protests.

JUST WATCHED President Trump teases pardon of Joe Arpaio Replay More Videos ... MUST WATCH President Trump teases pardon of Joe Arpaio 00:47

What were people upset about? Well, Trump was reportedly considering a pardon for recently convicted ex-sheriff Joseph Arpaio, whose anti-immigrant demagoguery has made him a living symbol of prejudice for many Americans.

Trump didn't announce an Arpaio pardon (although he essentially predicted it would happen) but his rally appearance marked a return of the performer who prefers ad-libbed assertions and insults to unifying leadership -- and discouraged anyone who'd hoped for better from the 45th president. Of course Trump has never made a secret of who he really is. He answered the question in 2016 when he said, on the subject of teleprompters:

"I've started to use them a little bit. They're not bad. You never get yourself in trouble when you use a teleprompter. You know, the problem is, it's too easy. We have a president who uses teleprompters. It's too easy. We should have non-teleprompter speeches only when you're running for president. You find out about people. The other way you don't find out about anybody."