Henrietta Treyz, the director of economic policy at the investment firm Veda Partners, said that lawmakers remained hopeful that the tariffs were a saber-rattling negotiating tactic and that markets would calm down when there was finally “certainty” about them. Investors, however, remain skittish.

“There is an emerging view on Capitol Hill that once we get past April 1, there will be certainty, and markets will calm down,” Ms. Treyz said. “That view is not shared by most investors who think the uncertainty is the near-term volatility driver but take the economic ramifications equally if not more seriously.”