President Trump took office 101 days ago after a campaign in which voters bought his argument that he could skillfully manage the economy and that his policy prescriptions could both bolster growth and eradicate inflation.

So the news on Wednesday that the nation’s gross domestic product had contracted in the first three months of the year was a sharp political jolt as well as a blinking economic warning.

It came at the end of a quarter in which stock prices were down sharply, Wall Street’s worst performance at the start of a new presidential term since Gerald R. Ford tried to steer the country out of scandal and inflation 51 years ago. And it only added to the widespread uncertainty among businesses and consumers about what the rest of the year might hold as Mr. Trump pursues a trade war that is already choking off supply chains and threatening to push prices up and lead to shortages of critical components and products on shelves.

It is too soon to predict where the American economy is headed for the rest of the year, and Mr. Trump remains insistent that he will produce a flurry of trade deals that will bring manufacturing back to the United States and usher in a new age of prosperity.

But the first-quarter figures brought the political risks for him into focus. For Mr. Trump, what is at stake is a question of fundamental competence on an issue that he has always used to define himself.

If the report proves to be a harbinger of an extended slowdown or recession, the situation could become the economic analog of President Joseph R. Biden Jr.’s fumbled withdrawal from Afghanistan four years ago this summer. Mr. Biden’s job approval ratings never recovered from that early debacle. Nothing he did later — not the millions of jobs created, not the big legislative victories, not the rapid response to Russia’s invasion of Ukraine — could restore the sense among voters that he could be trusted to carry out the job with the skill they assumed he brought to it.

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