COMMENTARY: Donald Trump has not yet been sworn in and the honeymoon has already come and gone

Presidents-elect usually lie low during the interregnum. Trump never lies low. He seized the actual presidency from Barack Obama within weeks of his election — cutting ostentatious deals with U.S. manufacturers to keep jobs at home, challenging 40-year-old China policy, getting into a very public fight with the intelligence agencies. By now he has taken over the presidential stage. It is true that we have only one president at a time, and for over a month it’s been Donald Trump.

The result is quantifiable. A Quinnipiac poll from Nov. 17-20 — the quiet, hope-and-change phase — showed a decided bump in Trump’s popularity and in general national optimism. It didn’t last long. In the latest Quinnipiac poll, the numbers have essentially returned to Trump’s (historically dismal) pre-election levels.

For several reasons. First, the refusal of an unbending left to accept the legitimacy of Trump’s victory. It’s not just the demonstrators chanting “not my president.” It is leading Democrats pushing one line after another to delegitimize the election, as in: he lost the popular vote, it’s James Comey’s fault, the Russians did it.

Second, Trump’s own instincts and inclinations, a thirst for attention that leads to hyperactivity. His need to dominate every news cycle feeds an almost compulsive tweet habit. It has placed him just about continuously at the center of the national conversation and not always to his benefit.

Trump simply can’t resist playground pushback. His tweets gave Meryl Streep’s Golden Globes screed priceless publicity. His mocking Arnold Schwarzenegger for bad “Apprentice” ratings — compared with “the ratings machine, DJT” — made Trump look small and Arnold (almost) sympathetic.

Nor is this behavior likely to change after the inauguration. It’s part of Trump’s character. Nothing negative goes unanswered because, for Trump, an unanswered slight has the air of concession or surrender.

Finally, it’s his chronic indiscipline, his jumping randomly from one subject to another without rhyme, reason or larger strategy. In a week packed with confirmation hearings and Russian hacking allegations, what was he doing meeting with Robert Kennedy Jr., an anti-vaccine activist pushing the thoroughly discredited idea that vaccines cause autism?

We know from way back during the Republican debates that Trump himself has dabbled in this dubious territory. One could, however, write it off as one of many campaign oddities that would surely fade away. Not so, apparently.

This is not good. The idea that vaccines cause autism originally arose in a 1998 paper in the medical journal The Lancet that was later found to be fraudulent and had to be retracted. Indeed, the lead researcher acted so egregiously that he was stripped of his medical license.

Kennedy says that Trump asked him to chair a commission about vaccine safety. While denying that, the transition team does say that the commission idea remains open. Either way, the damage is done. The anti-vaccine fanatics seek any validation. This indirect endorsement from Trump is immensely harmful.

Vaccination has prevented more childhood suffering and death than any other measure in history. With so many issues pressing, why even go there?

The vaccination issue was merely an exclamation point on the scatter-brained randomness of the Trump transition. All of which contributes to the harried, almost wearying feeling that we are already well into the Trump presidency.

Compare this to eight years ago and the near euphoria — overblown but nonetheless palpable — at the swearing-in of Barack Obama. Not since JFK had any new president enjoyed such genuine goodwill upon accession to office.

And yet it turns out that such auspicious beginnings are not at all predictive. We could see it this same week. Tuesday night, there stood Obama giving a farewell address that only underscored the failure of a presidency so bathed in optimism at its start.

The final speech, amazingly, could have been given, nearly unedited, in 2008. Why it even ended with “yes we can.”

Is there more powerful evidence of the emptiness of the intervening two terms? When your final statement is a reprise of your first, you have unwittingly confessed to being nothing more than a historical parenthesis.

Charles Krauthammer’s email address is letters@charleskrauthammer.com.