By PAUL WISEMAN and CHRISTOPHER RUGABER

WASHINGTON (AP) — When the stock market was climbing in January 2024, Donald Trump knew exactly who deserved credit: He did.

Nearly a year before his return to the White House, he declared on his Truth Social platform that investors were celebrating his lead in the polls against President Joe Biden.

When the stock market fell Wednesday on news that the American economy had gone backward during the first three months of 2025, Trump knew exactly who to blame: Biden.

“This is Biden’s Stock Market, not Trump’s,’’ he posted, adding that Biden “left us with bad numbers, but when the boom begins, it will be like no other. BE PATIENT!!!’’

Trump also said, “Our Country will boom, but we have to get rid of the Biden ‘Overhang.’ This will take a while, has NOTHING TO DO WITH TARIFFS.”

Yet for economists puzzling out how prices and hiring will change in the coming months, or businesses struggling with a starkly uncertain future, Trump’s massive and unpredictable import taxes on almost every country do in fact bear much of the blame. Rarely have a new president’s policies had such a sharp, immediate impact on the economy.

To Georgia Tech University’s Mark Zachary Taylor, who studies the economic policies of the American presidents, Trump’s assertions sound like a brazen double standard. “He cannot have it both ways,’’ Taylor said by email, “though he always tries.’’

Trump’s attempt to shift blame for bad economic news to his predecessor raises a question: At what point in a four-year term does a new president assume responsibility for the economy’s performance?

Commerce Secretary Howard Lutnick has said in interviews that the benefits of Trump’s policies will be felt in the second half of this year, particularly in the fourth quarter.

And Taylor notes that for a typical president, “it might take six months to two years for us to accurately call the economy ‘theirs.’”

But the threshold is different for presidents who enter the White House with big ambitions to reshape the economy from the get-go.

“The more boldly an incoming president acts (and the stronger his Congressional support), the sooner the economy becomes ‘his,’ ” Taylor said.

The most notable example is President Franklin D. Roosevelt, who pushed through major legislation — including a bill that effectively established deposit insurance to calm a banking crisis – to combat the Great Depression during his first 100 days in office. Presidents Ronald Reagan and Barack Obama also entered office during economic crises and moved swiftly to deal with them.

But even they did not move the economic data as quickly or sharply as Trump. On Wednesday, the government reported that imports surged 41%, the biggest jump — excluding the pandemic — since 1972. Companies rushed to bring in goods in the first quarter to beat the impending tariffs.

The flood of imports pulled down growth, under the government’s accounting, and the economy shrank 0.3% at an annual rate, the first decline in two years. The negative showing is what prompted Trump’s Biden-bashing post on Wednesday.

The figures are “exactly what one would expect from millions of American businesses and households trying to get ahead of looming tariff hikes,’’ Taylor said, adding that Trump’s trade war is also responsible for the slumping stock market and a drop in the value of the dollar.

Surveys show that manufacturers are receiving fewer orders and that their production is falling. On Thursday, the Institute for Supply Management, a trade group of purchasing managers, released its monthly survey of manufacturers, which typically includes a selection of comments from its membership.

Typically, the comments reflect the individual concerns of a specific industry, whether chemicals, electronics, or clothing makers. In April’s report, all 10 comments — every single one — focused on tariffs.

“Tariffs impacting operations — specifically, delayed border crossings and duties calculations that are complex and not completely understood,” one company in the transportation equipment sector said. “As a result, we are potentially overpaying duties.”

Trump has blown up the existing world trade system by slapping 10% import taxes – tariffs – on friends and foes alike in the name of bringing back jobs to the U.S. He’s plastered 145% tariffs on China, drawing retaliation from Beijing that threatens to end trade between the world’s two largest economies. He’s also hit foreign steel, aluminum and autos.

The erratic way he’s rolled out his protectionist policies – introducing, then suspending tariffs, then announcing new ones – has left companies, consumers and investors bewildered. The S&P 500 stock index has dropped 7% since just before Inauguration Day Jan. 20. And consumer confidence has wilted.

“Some of what you are seeing right now is purely Trump related,’’ said Columbia University’s Joseph Stiglitz, a Nobel Prize-winning economist and chair of the White House Council of Economic Advisers in the Clinton administration. “No one can look at what is going on in the economy without saying the on-again, off-again tariffs are not having an impact.