President Biden’s O.C.C. pick declares her support for capitalism and community banks.

Facing a room full of United States senators — some of whom have suggested she is a communist — Saule Omarova, President Biden’s pick to lead the Office of the Comptroller of the Currency, introduced herself by declaring that she loves two things: American capitalism and community banks.

Ms. Omarova, a Cornell Law School professor, appeared before the Senate Banking Committee on Thursday, the start of what will be a tough path to confirmation as the head of the regulator overseeing national banks. Soon after her nomination, bank lobbyists began an unusually strident campaign against her, echoing critics who cited her birthplace — Kazakhstan, a former Soviet republic — as a reason to question her loyalty to the United States.

Bankers claimed that her academic writing proved that she was poised to replace the banking system with a government-run alternative. Even members of the Senate Banking Committee, where Ms. Omarova is set to appear, joined in questioning her views: The committee’s highest-ranking Republican, Pat Toomey of Pennsylvania, repeatedly demanded to see Ms. Omarova’s master’s thesis to check it for Marxist ideas.

In a prepared opening statement, Ms. Omarova cast her background in the opposite light. She grew up, she said, with a grandmother who was orphaned when Stalin sent her family to Siberia for refusing to join the Communist Party.

She described the government during her childhood as an “oppressive state-run system, with no free enterprise and no economic opportunity for people like me.” Her ultimate dream, she said, became “coming to America — the land of opportunity and freedom.”

Much of the concerns raised by bankers and Ms. Omarova’s critics stems from her writings on topics such as how the Federal Reserve could use a central bank digital currency to expand access to banking services to Americans lacking bank accounts. The idea of a public banking option already has broad support among academics and progressive lawmakers, but bank lobbyists have said Ms. Omarova’s writing amounted to an existential threat.

“My concern with Professor Omarova is her long history of promoting ideas that she herself describes as ‘radical,’” Mr. Toomey said. “I agree that they are radical. But I’d also describe them as socialist. In fact, I’ve never seen a more radical nominee to be a federal regulator.”

Senator Sherrod Brown, an Ohio Democrat and the committee’s chairman, countered that the criticism of Ms. Omarova amounted to “McCarthyism.”

In her testimony, Ms. Omarova said her writings were intended to be “part of an ongoing academic debate.” During questioning from Senator Richard Shelby, Republican of Alabama, about her approach to regulation, Ms. Omarova said that her writings were intended to “think about how the financial regulators need to change their way of thinking, to broaden their way of thinking now that we are not dealing with regular old stock certificates written on paper but with digital technologies.”

Private banks, she said, were crucial to the American economy and must be protected. “I will never forget the first time I opened a checking account,” she said.

If confirmed, Ms. Omarova would lead the regulator that banks are looking to for clarity on how they can participate in cryptocurrency markets, as well as how they can more successfully compete with nonbank financial technology companies, or fintechs. She would most likely have to draft new rules for a decades-old anti-redlining law, the Community Reinvestment Act, and would be expected to help carry out Mr. Biden’s stated mission to get the financial industry to help combat economic inequality and climate change.

The committee will later vote on her nomination, and if it is approved there, it would face a full Senate vote.