The Consumer Financial Protection Bureau, which was born out of the 2010 Dodd-Frank Act, immediately seized on the payday lending industry as one of its first targets, opening a complaint database, initiating investigations, filing lawsuits and formulating rules to prevent lenders from preying on consumers. According to the consumer agency, it has pursued more than 20 public enforcement actions against small-dollar lenders, many of which have resulted in large settlements.

The crackdown has had an effect. According to data from the Center for Financial Services Information, annual payday lending revenue dropped to $5.3 billion in 2017, from $9.2 billion in 2012. The number of payday loan stores dropped from a peak of 24,043 in 2007, to 16,480 in 2015, according to a recent report published by the consumer bureau.

The industry has long been a presence on Capitol Hill, but it spied an opening after Mr. Trump’s election and the Republican takeover of Congress. The industry pushed lawmakers to repeal the consumer bureau’s 2017 payday lending rule by using the Congressional Review Act to essentially kill it. A bipartisan group of lawmakers has sponsored such a resolution, though its viability remains uncertain. Since Mr. Trump’s election, the payday lending lobby has also made its voice heard at the consumer bureau, flooding the agency with comments expressing opposition to the payday rule.

And lenders have poured money into the coffers of influential Republican lawmakers. Lobbying donations peaked in 2012, when the bureau began to make payday lending a priority and have leveled off in the last year. Among the biggest recipients have been Representative Jeb Hensarling of Texas, the Republican chairman of the House Financial Services Committee, and Senator Mike Crapo of Idaho, the Republican chairman of the Senate Banking Committee.

In December, Mr. Hensarling, who has long accused the consumer bureau of overreach, said that “no unelected Washington bureaucrat” should be able to stop Americans from taking out the short-term loan that they wanted.

Payday lenders have also looked for inroads with the president. A lender based in Ohio, Community Choice Financial, was one of the first clients of Corey Lewandowski, Mr. Trump’s first campaign manager, who started a Washington consulting business last year. Over the summer, Mr. Lewandowski called on Mr. Trump in a television interview to fire Mr. Cordray.