President Trump began his Wednesday with some advice for those rattled by his steep tariffs.
“BE COOL,” Mr. Trump told his followers on social media after the markets opened. Just a couple of minutes later he wrote, “THIS IS A GREAT TIME TO BUY!!!”
Hours after that, Mr. Trump sent the markets soaring when he paused the levies for 90 days. The S&P 500 climbed several percentage points in a matter of minutes and was on its way to its best day since the recovery of the 2008 financial crisis.
Soon after Mr. Trump’s pause, Democrats and government ethics experts asked the perhaps obvious question: Did Mr. Trump give the green light to his followers to cash in on a forthcoming rise in stock prices?
“How is this not market manipulation?” Representative Mike Levin, Democrat of California, said on social media, referring to action that is potentially illegal. “If you’re a Trump supporter and you did what he said and you bought, then you did great. On the other hand, if you’re a retiree or a senior or somebody in the middle class over the last few days that didn’t have the tolerance for risk and you decided to sell, you got screwed.”
The news of Mr. Trump’s pause came as Jamieson Greer, the U.S. trade representative, was testifying on Capitol Hill. Representative Steven Horsford, Democrat of Nevada, pressed him on Mr. Trump’s aim.
“It’s not market manipulation,” Mr. Greer said. “We’re trying to reset the global trading system.”
“How have you achieved any of that?” Mr. Horsford asked. “So if it’s not market manipulation, what is it? Who’s benefiting? What billionaire just got richer?”
White House officials have rejected such accusations as they have claimed that Mr. Trump’s post was meant to reassure Americans. They have tried to spin his decision to remove most of the tariffs as not a capitulation, but something that came only after some of China’s closest allies sought deals with the United States.
“It is the responsibility of the president of the United States to reassure the markets and Americans about their economic security in the face of nonstop media fear-mongering,” said Kush Desai, a White House spokesman. “Instead of grasping at straws to play partisan political games, Democrats should focus on working with the administration to restore American greatness.”
Senator Adam B. Schiff, Democrat of California, said he would reach out to the White House and seek to learn more about who knew of Mr. Trump’s impending decision to pause the tariffs. He said the flip-flop provided “dangerous opportunities for insider trading.”
“Did anyone buy or sell stocks, and profit at the public’s expense?” Mr. Schiff asked on social media.
Kathleen Clark, a professor focusing on government ethics and corruption at the Washington University School of Law in St. Louis, said Mr. Trump’s actions “would ordinarily trigger an investigation by the Securities and Exchange Commission.”
Such investigators would be looking for evidence that Mr. Trump knew he was going to make an announcement that would move the market and then provided a clue to his followers, Ms. Clark said.
“If we still had a rule of law, a robust system for the rule of law, it would be investigated,” she said.
In a statement, the S.E.C., which reviews possible violations of federal securities laws, declined to respond to questions about Mr. Trump’s post.
