WASHINGTON — At her confirmation hearing in early 2021, Treasury Secretary Janet L. Yellen told lawmakers that it was time to “act big” on a pandemic relief package, playing down concerns about deficits at a time of perpetually low interest rates and warning that inaction could mean widespread economic “scarring.”

A year and a half later, prices are soaring and interest rates are marching higher. As a result, Ms. Yellen’s role in crafting and selling the $1.9 trillion American Rescue Plan, which Congress passed in March of last year, is being parsed amid an intensifying blame game to determine who is responsible for the highest rates of inflation in 40 years. After months of pinning rising prices on temporary supply chain problems that would dissipate, Ms. Yellen acknowledged last week that she had gotten it “wrong,” putting the Biden administration on the defensive and thrusting herself into the middle of a political storm.

“I think I was wrong then about the path that inflation would take,” Ms. Yellen said in an interview with CNN, adding that the economy had faced unanticipated “shocks” that boosted food and energy prices.