Julian Zelizer is a history and public affairs professor at Princeton University and the author of " The Fierce Urgency of Now: Lyndon Johnson, Congress, and the Battle for the Great Society ." He's also the co-host of the " Politics & Polls " podcast. The opinions expressed in this commentary are his own.

(CNN) Until Saturday, President Donald Trump had earned some praise for his trip to Asia. Overall, the visit seemed to go well by the standards we use to evaluate him. There were few unsettling tweets over the past few days, at least relative to his normal routine, and by most accounts the meetings with the key leaders have gone smoothly. Trump has played ball in the diplomatic celebrations and seemed to be in good spirits. He's offered some provocative words about North Korea, but nothing that comes close to the kinds of incendiary words he used before the United Nations in New York.

Yet to call the trip a success would be a big mistake.

On Saturday, the President delivered his first moment of shock and awe with his Achilles' heel on foreign policy: Russia. In an act of defiance, he said he believed President Vladimir Putin's claim that Russia did not intervene in the 2016 US election despite all the evidence to the contrary, including from US intelligence agencies. He seems more worried that Putin is "insulted" by the accusations than he is by the impact these operations had on our democratic processes. The shocking comments about Putin are likely to drown out everything else that has happened so far.

The statement is a head-turner. It is part of the ongoing puzzle from this administration: What explains Trump's insistence on taking a relatively positive stance toward the Russian government despite the overwhelming evidence we have of an ongoing cyberwar against democratic elections and a terrible record on human rights.

There was no need for Trump to make this statement right now, and because it comes in the middle of special counsel Robert Mueller's investigation it will only fuel more questions about why the relationship with Putin seems so important to him.

While Trump backtracked on his statement during questions and answers with reporters by saying that he does believe the intelligence agencies, he left more than enough Trumpian ambiguity to give the impression that he is not taking this seriously.

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Trump continues to give legitimacy to a leader with a well-documented history of abusive behavior without any clear payback at this point -- as Richard Nixon sought with détente in the 1970s or Ronald Reagan with Mikhail Gorbachev in 1987. Nixon and Reagan each softened their tone toward the Soviets in exchange for major arms control agreements -- although neither ever ignored the underside of communism. Indeed, they were both careful to acknowledge publicly the unacceptable parts of Soviet behavior so they could enter into the negotiations with legitimacy among US allies and so that the Soviets understood the United States would not simply cave to every demand. Trump has systematically undercut the efforts of previous presidents and the current Congress to intensify pressure on Russia. Instead, as he has now done on this trip, he is Putin's ally-in-chief.

The irony is that his laggard response to Putin's abuses and the ongoing revelations about what his campaign and administration officials hid about their relations to Russia taints all efforts to work with Russia on issues such as Syria. Every negotiation becomes suspect -- not because of the media but because of Trump and his team.

Nor can Trump overcome the wreckage he has left behind in the United States. Since he left for Asia, the news has been pretty devastating for himself and the Republican Party. We learned that Mueller's investigation has intensified with two indictments, one guilty plea and recent reports about the possible new directions of the investigation into former national security adviser Michael Flynn.

recent round of polling has shown that Trump has historically low approval ratings at this point in his presidency. Many Americans don't trust the President and believe he might have done something wrong in his dealings with Russia.

Independents are not happy with the administration, and even in Trump counties, according to The Wall Street Journal, many feel the country is worse off since he took office.

Tuesday's elections sent shockwaves through the GOP. Democrats turned out in large numbers, with many choosing to send a signal of opposition to Trump through their own local elections. The possibility of a Democratic coalition of suburban voters, African-Americans, women, Latinos and millennials emerged to counteract the Trump coalition of white, rural, noncollege-educated voters.

Foreign leaders pay attention to these things. In person, they might be pleasant with the President and avoid any uncomfortable subjects, but Trump's domestic standing matters very much in terms of his clout. When they look at the news in the United States they see a greatly weakened President who will probably not have the capacity to deliver on many things or to rally the support of the nation behind any military or diplomatic initiative. This fact continues to hobble how much Trump can achieve overseas, and the situation has only deteriorated during this trip.

Finally, there is the problematic nature of the overall message that the President has delivered: The United States is demanding a full and united front against the threat of North Korea but will not participate in comprehensive, regional trade agreements. This message, which Trump has been consistent about, is devastating.

Trump is reversing the basic strategy of President Barack Obama, which had been to increase the leverage of the United States in Asia through participation in a trade agreement. The idea was that once the United States was more closely tied to the key players in the region through trade, then we could enhance our ability to sway governments, including China, which would respond to our more muscular economic presence in the region, on security issues such as North Korea.

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Trump blew this apart when he pulled out of the Trans-Pacific Partnership and then continued to tell Asian leaders the United States would not enter into any comparable agreements.

At the summit of Pacific Rim leaders, he said, "I am always going to put America first. ..." The problem with this approach is that it leaves the United States without any serious leverage in the region, and it doesn't give countries such as China good reason to work with the US if our demands don't fit their interests. "For Trump to come with an ' America First ' agenda leaves Asian leaders in the lurch," one expert told The New York Times.

Nor has the President done much to inspire confidence that his "Indo-Pacific" strategy has any substance. As has been the case with the Paris climate accord and possibly the Iran nuclear deal, Trump keeps isolating the United States rather than our adversaries by removing our government from these international agreements.

And for any Trump loyalists who feared their hero had been sanitized, they can put their worries to rest. President Trump let loose with a vicious tweet storm calling Kim Jong-Un "short and fat" and bringing up "Crooked Hillary." He called ex-intelligence leaders who tracked Russian intervention "political hacks."

The President completes his tour as an extraordinarily weak leader politically who does not have the muscle at home to move debates in the direction he wants. The visit might have looked and sounded better than many observers expected, but, in the end, it did not add up to much.

Editor's note: This article has been updated with news of new tweets and comments by President Trump.