WASHINGTON — President Barack Obama has chosen Elisse Walter, one of five members of the Securities and Exchange Commission, to head the agency. Chairman Mary Schapiro will leave next month after a tumultuous tenure in which she helped lead the government’s regulatory response to the financial crisis.

Walter will take over at a critical time for the SEC, which is finalizing new rules in response to the 2008 crisis. She can serve through 2013 without Senate approval because she’s already been confirmed to the commission.

Obama will need to nominate a permanent successor before Walter’s term ends in December 2013. News reports have suggested that Mary John Miller, a top Treasury Department official, might be a potential candidate.

Walter, 62, a Democrat, was appointed to the SEC in 2008 by President George W. Bush. Earlier, she was a senior official at the Financial Industry Regulatory Authority, the securities industry’s self-policing organization. She served under Schapiro at FINRA, who led that group before becoming SEC chairman in January 2009.

“I’m confident that Elisse’s years of experience will serve her well in her new position,” Obama said in a statement.

Walter is likely to follow the path Schapiro established at the SEC, experts suggested.

At FINRA, Walter was Schapiro’s “right-hand person,” said James Cox, a Duke University law professor and expert on securities law. And as an SEC commissioner, Walter consistently voted with Schapiro on rule makings and other initiatives.

Cox said he wasn’t surprised that both of Obama’s choices to lead the SEC have come from an industry self-regulatory organization.

The Obama administration “is not an eager regulator of the securities markets,” he said.