NEW YORK — Mary Jo White, the head of the Securities and Exchange Commission, announced Monday that she will step down two years before the end of her term, clearing the way for President-elect Donald Trump to reshape the way Wall Street is regulated.

The SEC, which polices Wall Street and the financial markets, has been a key part of the Obama administration’s effort to rein in big banks following the 2008 financial crisis and prevent future taxpayer bailouts of the industry. The agency has pushed for more oversight of hedge funds and other asset managers and has established rules that make it more difficult for big banks to make risky bets on the markets.

White, a former federal prosecutor, is known for a no-nonsense style and beefed up the agency’s enforcement efforts over the last three years, pushing for more companies to admit guilt and taking more cases to trial. But progressive Democrats were often critical of her efforts, complaining they did not go far enough. White was widely expected to step down no matter who won the election to allow the next president to appoint their own chair.

Trump has already indicated he would usher in a period of deregulation, including dismantling 2010’s financial reform legislation, known as the Dodd-Frank Act. He appointed Paul Atkins, an industry veteran, who has called Dodd-Frank a “calamity,” to lead the agency’s transition.

Atkins “is a guy in general who wants to let companies do their thing and not get in the way very much,” Ian Katz, a financial policy analyst with the research firm Capital Alpha Partners, said of Atkins. “You would see a lighter touch on enforcement and a lighter hand on corporate governance issue broadly.”

Atkins served as an SEC commissioner for six years during the President George W. Bush administration. He could not immediately be reached for comment.

In addition to replacing White, Trump will be able to fill two openings on the five-member commission. Trump could also choose to ignore the more than 20-year-old tradition of allowing the opposing political party to pick its own representative on the commission, one industry official said, further bolstering his influence over the agency. Also, Thomas Curry, the head of the Office of the Comptroller of the Currency, another important Wall Street regulator, has less than six months on his term. Together, the openings should give the Trump administration wide latitude to change the way Wall Street is regulated.

“It is a game-changer at the SEC. The commission is going to have a very different agenda over the next four years than it would have,” said Edward Mills, a policy analyst at investment bank FBR Capital Markets. “In the long-term, it is going to be a big tilt towards free markets.”

White took office with high expectations. The SEC had long suffered under the popular notion that it was a slow, toothless tiger. White appeared to be someone who might change that reputation. Prior to her appointment, she had been a federal prosecutor who took on the terrorists behind the bombing of the World Trade Center in 1993 and the Mafia boss John Gotti.

“You don’t want to mess with Mary Jo,” President Obama proclaimed while announcing her nomination in 2013.

White moved quickly to set a new tone at the agency. Soon after taking office, she announced that the SEC would begin requiring more companies to admit guilt as part of their settlements with the agency. It was a break from the SEC’s nearly 100-year history of extracting monetary penalties from companies, which typically would neither admit nor deny the charges lodged against them.

“The SEC had more leverage than it realized,” White said in a recent interview. Not requiring admissions of guilt could “undermine, at least, the perception of the strength of a settlement, the strength of its deterrence. In certain cases that public accountability, I think, is very important.”

Critics would later complain that many large banks were still able to settle SEC cases without admitting guilt and that the agency’s toughest actions were reserved for smaller banks.

The SEC also poured resources into improving its technical capabilities, hiring experts who could help it better track stock trading and catch fraud. The SEC’s technical capabilities have “really been transformed over the last three years,” White said. There have been several cases, including some involving insider trading, that would have been impossible without these advancements, she said. Examinations of trading patterns that used to take months can now be done in hours, she said.

But in the years since, the SEC has also been overwhelmed by the task of implementing dozens of rules called for under the 2010 Dodd-Frank financial reform law and the 2012 JOBS Act, which aims to make it easier for small businesses to raise money. The 4,000-person agency has tussled repeatedly with Congress and complained that as Wall Street became more complex it needed a bigger budget to keep up.

White ultimately became a target of progressive groups that questioned her resolve to crack down on Wall Street. In addition to serving as a prosecutor, White also spent years defending big banks, including Bank of America and JPMorgan Chase, as a white-collar lawyer, they noted. And while White trumpeted that she had secured settlements with nearly 90 high-level executives for financial-crisis related misdeeds, critics noted that officials at some of the country’s largest banks had emerged largely unscathed.

Last year, CREDO Action, a liberal advocacy group, sent a  “Dump (Mary Jo) Truck” around D.C. to mark the anniversary of the collapse of Lehman Brothers.

Another group put up billboards in the D.C. Metro system depicting White as a superhero missing in action and asking “Where is Mary Jo White?”

White’s unpopularity among some progressive Democrats was particularly pronounced when she found herself the target of Sen. Elizabeth Warren (D-Mass.).

In January, Warren issued a report arguing that U.S. companies get away with crimes that regular people don’t because of weak enforcement. The SEC “is particularly feeble, often failing to use the full range of its enforcement toolbox,” the report said.

Then in June, Warren and White faced off during a Senate Banking Committee hearing. “A year ago I called your leadership at the SEC extremely disappointing,” Warren said. “Today I am more disappointed than ever.”

White quipped: “I’m disappointed in your disappointment.”

But White’s supporters, including many industry officials, say the criticism has been unwarranted.

“As SEC chairs go, Mary Jo has been one of the very best,” said Harvey Pitt, who was SEC chairman under President George W. Bush. “No one in that position will go uncriticized. But, in my view, the criticism has been completely unwarranted.”

White plans to formally depart when Obama leaves office.