(CNN) President Donald Trump tried to explain his agitating approach to life, politics and the rest of the world in a flash of impatience during a blustery news conference in France .

"It's the way I negotiate. It's done me well over the years and it's doing even better for the country, I think," he said.

Trump's comment encapsulated the untamed personality that his fellow world leaders are beginning to get used to -- and work around after his 29 months in office.

But in a deeper sense, Trump also shed light on fundamental judgments about his tenure that voters must make before the 2020 election.

His political future could rest on whether a sufficient number of Americans decide that the Trumpian tumult of his first term expresses their frustration with the Washington establishment and has delivered the wealth, peace and patriotic pride that he promised in the 2016 campaign.

One big risk is that a majority of voters may simply be exhausted by the cacophony of the Trump era t hat was on display at the weekend at the G7 summit in France and involves chaos , head-spinning policy reversals, lying as a matter of course, perpetual cultural warfare and widening national divides.

In other words, is all Trump, all the time, "doing even better for the country" as the President insists?

A wild weekend

The President's weekend in Biarritz, France, was a classic example of his behavior overseas.

His policy choices on Iran, climate, trade with China and trying to get Russian President Vladimir Putin back into the summit despite the opposition of US allies, left America isolated on the global stage.

Yet his belligerence was also undeniably an expression of US power since foreign leaders who might not be able to live with Trump but can't live without America tried not to annoy him. True to his word, the President has made the world's most powerful nation unpredictable, leaving friends and rivals unsure of what it will do next.

And he made a series of bizarre claims and assertions that left his aides struggling to shape believable explanations -- including whether first lady Melania Trump had met North Korean dictator Kim Jong Un. ( She has not, it turns out .)

Above all, Trump's behavior underscored how his combustible personality has transformed the United States from being one of the world's most stable influences into one of its most disruptive forces.

It was notable how summit host French President Emmanuel Macron played a stabilizing and convening role at the weekend, inserting his nation into the spot of the mature global power once reserved for the United States.

Trump chose instead to wage the bellicose daily combat that characterizes most days when he is at home in the White House and that has become the soundtrack of life in America.

Trump's base loves what he's doing

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Trump made another notable comment in Biarritz.

"I don't do things for political reasons," he said in one of the least credible utterances of a presidency in which almost every decision seems calculated to please his most loyal voters.

After landing back in Washington on Tuesday night, Trump tweeted a highly produced campaign-style video showing him side-by-side with world leaders that suggested that he was at the center of events unifying the G7 -- even though in terms of policy and temperament he was often on the outside.

While Trump's behavior horrifies the East Coast establishment, his bull-in-a-china shop performance in France is the key to his appeal among the Trump base.

Upsetting leaders of states whom Trump thinks have long exploited US generosity and defense guarantees is just fine with the "Make America Great Again" fans who flock to his rallies. Trump's statement on climate change -- that he won't lose US wealth on "dreams, on windmills" -- was calculated to play to his blue-collar supporters in industrial Midwest swing states.

The President's "America First" policy in which the US wins and other states lose has proven to be an effective political strategy among voters who support the President.

Some conservative media, meanwhile, took at face value his comments on Monday morning that China had got in touch overnight for new talks -- playing into his claims of being a great dealmaker even though an objective analysis might find little support for such claims.

Trump's relentless attack on the media, including a tweet which claimed improbably that world leaders had asked him why reporters hated America, also plays well with his base. While he peddles obvious falsehoods -- for instance, over the reasons why Russia was thrown out of the G8 summit -- his long crusade against what he calls "fake news" means that his supporters are disposed to believe whatever he says.

How Trump isn't 'doing better' for America

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But there were also signs in recent days that Trump's erratic methods are catching up with him.

His gyrations over China -- from fury to adopting a softly softly approach and buttering up Chinese President Xi Jinping -- have left his strategy on the trade war mired in confusion. Barring an unlikely climbdown by either side, there is no obvious way out of an escalation that could damage the world economy, hurt US consumers and prejudice Trump's reelection hopes.

Trump's unrestrained behavior also took the focus off some of the weekend successes that could benefit his 2020 campaign.

He agreed with Japanese Prime Minister Shinzo Abe that the two sides are close to a trade deal. While there are many details that are unclear about the scope of the pact, it would be a strong data point for him to trumpet on the campaign trail -- even if, like other Trump-era trade agreements, it fails to live up to his spin.

Trump's careful openness to a French effort to broker a meeting with Iranian President Hassan Rouhani could be spun as a potential sign of statesmanship and a payoff for his maximum pressure campaign and cool fears of war.

Yet the story of Trump's latest world trip concerned the apparent instability of his character, the coherence of his White House messaging and whether he was up to the job.

The President's habitual challenges to the truth may also be hurting his foreign policy.

When the word of a communist Chinese government is trusted as much among such an audience as that of a pro-business Republican President, it's a sign of how Trump's reshaping of truth has cost him politically.

Foreign policy rarely decides elections. And Trump's performance at the G7 summit will be a distant memory in November 2020.

But his showing in France does help clarify the choice for those voters who are undecided about Trump and adds to a mountain of evidence about his character and fitness for office. Trump's unsteady performance was the latest example of his conduct that left him open to ridicule abroad. There was more ammunition for his critics on this score last week when he canceled a separate trip to Denmark because its prime minister would not sell Greenland to the US.

Democratic presidential candidates -- especially former Vice President Joe Biden -- are using such infringements of international etiquette to build their case that Trump is an embarrassment as America's outside face to the world and is therefore not fit for a second term.

"After three days of meetings in Biarritz, we have even more evidence of how President Trump's disastrous foreign policy has left the United States isolated while the world moves on without us," Biden said in a statement on Tuesday after observing a moratorium on criticism of the President while Trump was overseas.

"Rather than looking to America for vision, agenda setting, and leadership by example, our closest democratic allies sought to manage and mitigate the damage Trump might do at this year's G7," Biden said.

The former vice president said there was no more telling symbol of Trump's abdication of global leadership than the "empty chair" at the G7 climate talks.