Mild-mannered, lawyerly and with a genius for trivia, Richard Cordray is not the sort of guy you picture at the center of Washington’s bitter partisan wars over regulation and consumer safeguards.

But there he is, a 57-year-old Buckeye who friends say prefers his hometown diner to a fancy political reception, testifying in hearing after hearing on Capitol Hill about the agency he leads, the Consumer Financial Protection Bureau. Republicans would like to do away with it — and with him, arguing that the agency should be led by a commission rather than one person.

And with a Republican sweep of Congress and the White House, they may get some or all of what they wish.

Mr. Cordray, a reluctant Washingtonian who has commuted here for six years from Grove City, Ohio, where his wife and twin children live, is the first director of the consumer watchdog agency, which was created in 2010 after Wall Street’s meltdown. By aggressively deploying his small army of workers — he has 1,600 of them — Mr. Cordray has turned the fledgling agency into one of Washington’s most powerful and pugnacious regulators.

The bureau has overhauled mortgage lending rules, reined in abusive debt collectors, prosecuted hundreds of companies and extracted nearly $12 billion from businesses in the form of canceled debts and consumer refunds. In September, it exposed the extent of Wells Fargo’s creation of two million fraudulent customer accounts, igniting a scandal that provoked widespread outrage and toppled the company’s chief executive.

And, according to Mr. Cordray, he and his team have barely scratched the surface of combating consumer abuse.

“We overcame momentous challenges — just building an agency from scratch, let alone one that deals with such a large sector of the economy,” Mr. Cordray said in an interview at his agency’s office here. “I’m satisfied with the progress we have made, but I’m not satisfied in the sense that there’s a lot more progress to be made. There’s still a lot to be done.”

But his future and the agency’s are uncertain. Democrats in Ohio are encouraging Mr. Cordray to run for governor in 2018, which would require him to quit his job in Washington fairly soon, rather than when his term ends in mid-2018. Champions of the agency are imploring him to stay, arguing that if he leaves, the agency is likely to be defanged, its powers to help consumers sapped.

Opponents of the bureau just won a big legal victory: The United States Court of Appeals for the District of Columbia Circuit said last month that the structure of the Consumer Financial Protection Bureau was unconstitutional, and that the president should have the power to fire its director at will.

The agency is challenging the decision — which was made in a lawsuit brought by the mortgage lender PHH Corporation that contests the consumer bureau’s authority to fine it — and that has temporarily stopped the decision from taking effect. But the ruling has kept alive questions about whether too much power is concentrated in Mr. Cordray’s job, and whether the agency should be dismantled or restructured.

Mr. Cordray, who also battled on behalf of consumers in his previous jobs as Ohio’s attorney general and, before that, its treasurer, is praised in some circles as enormously effective, wielding the bureau’s power to restructure some industries and terrify others.

The bureau has “helped save countless people across the country from abusive financial practices,” said Hilary O. Shelton, the N.A.A.C.P.’s senior vice president for advocacy and policy.

Even the regulator’s frequent foes — including Alan S. Kaplinsky, a partner at Ballard Spahr in Philadelphia, who says the agency often overreaches — acknowledge its impact.

“I’ve been practicing law in this area for well over 40 years, and there’s nothing that compares to it,” Mr. Kaplinsky said. “Every company in the consumer financial services market has felt the effects.”

The Consumer Financial Protection Bureau has nearly replaced the Better Business Bureau as the first stop for dissatisfied customers seeking redress. It has handled more than a million complaints, many of which it has helped resolve.

*     *    *

The housing crisis dominated the bureau’s early days. When Congress created the new overseer, it also dictated its first priority: making mortgages safer. The deadline was tight. If the bureau did not introduce new rules within 18 months, a congressionally mandated set of lending guidelines would automatically take effect.

The bureau made it with one day to spare.

It banned some practices that had fueled the crisis, like home loans with low teaser rates or no documentation of the borrower’s income, and steered lenders toward “qualified” loans with a stricter set of safeguards, including checks to ensure that customers could afford to repay what they borrowed.

After much grumbling — and many dire forecasts that the new rules would limit credit and harm consumers — mortgage lenders adjusted. They made nearly 3.7 million loans last year for home purchases, the highest number since 2007, according to government data.

“It seems like the financial services industry has figured out how to adapt to this new regulatory regime,” said David Reiss, a professor at Brooklyn Law School who studied the effects of the bureau’s rule-making. “We’ve moved from the fox-in-the-henhouse market in the early 2000s, where you could get away with nearly anything, to this new model, where someone is looking over your shoulder.”