Trump has taken Putin's side. His stability and America's safety are now in question. Donald Trump has taken a side and it's not ours. He waltzed into a media event with Vladimir Putin, a professional intelligence officer, and imperiled America.

Tom Nichols | Opinion columnist

Show Caption Hide Caption Trump accepts Russia's denial of 2016 election meddling U.S. lawmakers are criticizing President Trump, saying he missed an opportunity to hold Russia accountable for meddling in the 2016 U.S. election.

The Helsinki summit is over, and we are all left struggling to find the words to capture the nightmare that in the space of less than 24 hours destroyed years of American diplomacy, sacrifice and leadership.

So perhaps we should just admit what our own eyes cannot deny: We have now witnessed the very worst humiliation of a president of the United States ever, and one of the lowest points in the history of the American presidency.

The summit was completely in Russian President Vladimir Putin’s control, and it showed. That was to be expected from an incompetent leader believing he could waltz unprepared into a news media event with a professional intelligence officer. A summit without an agenda is a bad idea from the start, but President Donald Trump clearly wanted to replicate the artificial media high of his trip to Singapore to meet North Korean leader Kim Jong Un — another disgraceful episode in itself — and garner high ratings and hollow applause from his usual fans and camp-followers.

But Kim is a young and relatively inexperienced brute, whose personal stature and weird mien do not play all that well on television. And all Kim needed to do was share a stage with an American president to accomplish his mission. Kim is crude and dangerous, but he is an amateur.­­­

Putin was careful and icily competent

Putin, however, is no amateur. He performed brilliantly, turning every issue back to the Americans, and Trump took it all. Ukraine? The Americans should talk to their Ukrainian friends, not us. Espionage? Pish-posh. We’re not that kind of country, but if you’d like us to look into it, hand over Putin opponent Bill Browder. Syria? Of course, we’d love to remain involved there under the guise of humanitarian aid, thank you for the invitation. Putin did what one would expect him to do, and his behavior was icily competent and carefully executed.

Trump, who understands none of these issues, stood there waiting for his few openings to plead his usual litany of insecurity and victimhood. Things have never been worse, Trump said, although Harry Truman, John F. Kennedy and Ronald Reagan, who weathered the Berlin Blockade, the Cuban missile crisis, and the 1983 war scare, would probably disagree. It’s doubtful Trump knows about any of those things, as they happened long ago and did not directly involve him personally, and therefore are not important.

Had the summit ended before the two leaders took any questions, it would have been a U.S. defeat, largely because it gave Putin a chance to refute all charges against his regime and to stand — like Kim — on a stage with the putative leader of the Free World after directing multiple attacks on the U.S. and its allies.

Once the questions began, Trump's behavior was not only shameful, but bizarre and seriously worrisome. The president of the United States not only sided with the Russian president, but he did so against the American intelligence community, the American law enforcement community, and the American system of justice.

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Why is Trump so enthralled by Putin? What does the Russian president have on him?

Given an opportunity to hold Russia accountable for anything — anything at all — the president instantly equivocated, blaming both countries. He babbled, literally, about servers. He attacked Democrats. He rambled about the Electoral College. He revealed, again, his obsession with Hillary Clinton, and noted that in Russia, no one would have lost her emails.

Putin, meanwhile, was serene, as well he should have been. He chuckled warmly as he instructed us all in the nature of intelligence tradecraft. "Do you think that we try to collect compromising material (on all high-ranking American businessmen)?" Of course the Russians do this. The only person in the world who doesn’t seem to understand this is Trump. Instead, responding to whether Putin had "compromising material" on him, he ran to Putin’s defense — and his own: If they had it, "it would have been out long ago." That’s not only a stupid dare, but a statement that could come back to haunt Trump.

By the end of this circus, Trump was practically mewling, begging for Putin's approval, saying that Putin's denials were "extremely strong and powerful," almost in a kind of strangely erotic tone of admiration.

The very last thing the president of the United States did at a summit with the Russian president was to attack an FBI agent. His last words, just before "thank you," were "witch hunt." Putin could not have scripted it better.

Trump stability, US safety in question

Every single person involved in this fiasco — national security adviser John Bolton chief among them — should be given no rest from questions about why this happened, what they intend to do now, and whether they think they can still serve the president now that he has unveiled a new policy of no-limits appeasement.

Meanwhile, Trump's performance will raise concerns not only about the president's personal stability, but about the future and safety of the United States and its allies that will last long beyond this moment. Trump thinks he solved everything in four hours, but we are all now in more danger than we were a day ago.

The Russians, at this moment, continue to attack us and they will attempt to interfere in the 2018 elections. Dan Coats, the director of national intelligence, has told us point-blank that all of the warning lights of an impending attack of some kind are flashing red, which is not language that the DNI — and a Trump ally — would use lightly. If Putin now thinks he can act against the U.S. and NATO with impunity, as he surely must, then we are headed for one of the most dangerous periods since the end of the Cold War.

But the president, the commander in chief of our armed forces, the man whose oath requires him to defend us, has taken sides. He has taken Putin’s side. We are in significant peril, and it will not abate soon.

Tom Nichols, a professor of national security affairs at the Naval War College and an instructor at the Harvard Extension School, is the author of "The Death of Expertise." The views expressed here are solely his own. Follow him on Twitter: @RadioFreeTom.