In 1973, when Donald J. Trump’s real estate firm faced a potentially existential threat from the Department of Housing and Urban Development’s accusations of discriminatory practices, his lawyer, Roy Cohn, filed a countersuit against the government, accusing the agency of defamation.
The gambit, announced at a news conference, helped Mr. Trump, then 27, slow down the HUD legal action, buy time and eventually claim a victory when, two years later, he signed a consent agreement with no admission of guilt.
The president has used that approach ever since, suing governments, banks, former employees and former business partners — even when there appeared to be no grounds — if he thought it would give him some tactical advantage.
Now, as the Democrat-controlled House tries to pry open the financial records of Mr. Trump and his businesses, lawmakers are finding themselves up against the same familiar tactics, along with a bevy of other actions from the Trump administration meant to halt their work. They are struggling to figure out how to respond to a president who refuses to recognize the norms of his office — or, they argue, the institutional authority of a coequal branch of government.
On Monday, Mr. Trump, three of his adult children and his company filed suit against two financial institutions subpoenaed by House Democrats seeking the president’s records. The move was meant to stop Deutsche Bank and Capital One from turning over those records, which Mr. Trump’s family and advisers say was an overly broad request.
Timothy L. O’Brien, the author of “TrumpNation: The Art of Being The Donald,” who was sued by Mr. Trump years ago for his characterization of the real estate developer’s personal wealth, said that the countersuit in 1973 taught Mr. Trump a lesson he did not forget.
“It’s the moment in which Roy Cohn teaches him that you can throw sand in the gears of any kind of scrutiny or enforcement action if you’re willing to hit back hard in the courts and make any kind of wild claims about the people coming after you,” Mr. O’Brien said.
In the suit filed this week, Mr. Trump’s lawyers accused House Democrats of making a number of statements about investigating him, some of which were either taken out of context or misattributed. They accused the lawmakers of targeting a “private citizen,” despite the fact he is president. And they said the documents sought included some for accounts linked to underage relatives of Mr. Trump’s, which they said could serve no relevant purpose.
The lawyers also said that the subpoenas serve no legislative function, and are merely political tools to “harass” the president.
Mr. Trump’s entire legal team and family were on board with the suit, as well as with one the Trumps filed a week earlier to keep the president’s longtime accounting firm, Mazars USA, from responding to congressional subpoenas, according to people familiar with the strategy. No one took convincing.
“We’re not going to sit idly by with congressional presidential harassment and overreach,” said Jay Sekulow, one of Mr. Trump’s personal lawyers. “The requests for information have raised serious constitutional issues that don’t just impact this president, but future presidents. We’re not allowing a congressional free-for-all.”
Stephen I. Vladeck, a professor at the University of Texas School of Law, said that there was precedent for people who believe congressional subpoenas may be overly intrusive seeking help from the courts.
“It’s a long shot on the merits, but it’s not frivolous,” Mr. Vladeck said of the suit.
The congressional committees are only the latest targets Mr. Trump has sued, countersued or threatened to sue. They include former and current friends, like the casino magnate Steve Wynn; media figures and news outlets; the National Football League; and former employees of his campaign or the White House.
A running tally from USA Today found that Mr. Trump has been connected to more than 4,000 lawsuits over three decades.
Like others targeted in Trump lawsuits past, the latest legal offensive has left Democrats scrambling to calibrate a public relations and legal response. Even if the lawsuits are unlikely to succeed in court, they believe, they may still succeed in the meantime in discouraging the cooperation of congressional witnesses and strengthening the president’s resistance.
But the challenge to Democrats is greater, in part, because of Mr. Trump’s apparent disregard for the precedent and procedures that typically govern one branch of government’s oversight of another.
Presidents from both parties have done their best to defy and limit Congress’s access to executive branch information in recent decades, but ultimately they have played by a set of unwritten rules that after leverage like subpoenas, budget appropriations and the possibility of public shaming have been deployed, the two sides meet somewhere in the middle.
Jason Chaffetz, Republican of Utah and the chairman of the House oversight panel during Barack Obama’s presidency, said Mr. Trump’s actions reflected an understanding that congressional subpoenas have been losing power for years.
“Your subpoena is only as good as your ability to enforce it,” Mr. Chaffetz said, “and the reality is the only way to enforce a subpoena is through the Department of Justice, so good luck with that.”
At least so far, Mr. Trump has chosen not to compromise with his Democratic investigators.
“He doesn’t care about any of that stuff,” Mr. O’Brien said. His Democratic critics, Mr. O’Brien said, “have no leverage over his conscience.”
Representative Maxine Waters, Democrat of California and the chairwoman of the House Financial Services Committee, told reporters on Tuesday that the latest lawsuit targeting her committee’s subpoena only highlighted questions about what in his financial history the president was so determined to hide from public view. Democrats, she said, would fight him “tooth and nail.”
“He may file the lawsuit,” Ms. Waters said, “but that is not the end of this game.”
Democrats are contemplating a range of responses. They could go to court themselves to try to seek orders enforcing the subpoenas. They could hold administration officials or other witnesses in contempt of Congress. Or they could initiative impeachment proceedings against Mr. Trump or other officials.
They appear determined to continue their financial investigations, as well. The House Intelligence Committee, one of the panels behind the subpoenas, has hired Patrick Fallon, the former head of the F.B.I.’s financial crimes unit, to aid the effort, according to a committee official who was not authorized to discuss it publicly.
“At the end of the day, Congress’s remedies here are legislation and impeachment,” Mr. Vladeck said.
But each has limitations, and even if Democrats are successful in ultimately getting ahold of the evidence and testimony they seek, Mr. Trump’s actions could slow their investigations. Mr. Vladeck said the delay would depend on the rulings of the judge overseeing the case, but he noted that if it goes through an appeals process, that could lead to significant delays.
“If you really think about it, I was being sued for doing my job,” said Representative Elijah E. Cummings of Maryland, the chairman of the Oversight and Reform Committee, whose subpoena of Mazars USA prompted the lawsuit last week.
“America needs to pay close attention when the American people have sent to Washington — a Democratic Congress to act as a check on the president and to make him accountable — and then he does things to block us from getting information,” Mr. Cummings said.
Republicans in Congress have presented Democrats with their own obstacles. In addition from casting Democrats as politically craven and illegitimate, for example, Representative Jim Jordan of Ohio, the top Republican on the oversight panel, has written to the subjects of multiple Democratic document requests to urge them not to comply.
Finding such allies was one of the lessons that Mr. Trump learned from Mr. Cohn.
Mr. O’Brien, the biographer, recalled that Mr. Trump’s father, Fred Trump, was the focus of congressional and state hearings over accusations that he profiteered off publicly funded subsidies. But Fred Trump did not fight the government and accepted being shut out of subsidy programs, Mr. O’Brien said.
“Then, the government comes after the Trump Organization in 1973 alleging discrimination — most people of Fred’s ilk would have said, ‘Pay your fine and move on,’” Mr. O’Brien said.
“Donald, I think with Roy baiting him,” chose another path, he said.