WASHINGTON — House Republicans on Saturday offered the latest glimpse of their strategy to fight against impeachment by demanding testimony from figures at the center of President Trump’s favorite unsubstantiated theories: the son of former Vice President Joseph R. Biden Jr., a researcher loosely connected to an anti-Trump dossier, a Democratic official and a board member of a Ukrainian energy company.
Rather than shy away from conspiracies that Mr. Trump’s own government has repeatedly disavowed or played down, the Republicans’ requests suggest their willingness to conduct a scorched-earth strategy as they respond to nearly a month of blockbuster revelations about pressure campaigns involving military aid, diplomatic shakedowns and rogue actions by the president’s personal lawyer.
Much of the witness list is certain to be rejected by Democrats leading the impeachment inquiry. But even if Republicans fail to get Mr. Biden’s son or the others under oath and in front of cameras, such attention-grabbing tactics by some lawmakers could appeal to Mr. Trump, stoke energy among his most loyal supporters and lend legitimacy to the president’s demand that Ukraine investigate many of the same people.
At the same time, the party is preparing to vigorously contest the Democratic case for impeachment on its own terms, people familiar with the plans said. As public hearings begin next week, members are focused on what they believe are major deficiencies in the evidence already collected.
Buoyed by their growing belief that Democrats have failed to find direct evidence of presidential misconduct, Republicans will insist that the president’s critics have gathered in closed-door testimony nothing more damning than secondhand accounts of wrongdoing that fall far short of impeachable offenses.
“Once again, the Democrats have overstated the case against the president,” Representative Mark Meadows, Republican of North Carolina, who has listened to hours of private depositions, said in an interview on Saturday. “They have led with their best witnesses and their best evidence, and it won’t stand the test of other evidence and cross-examination.”
The Republican optimism is certain to be tested as Democrats marshal the power of their majority to potentially impeach a sitting president for only the third time in the nation’s 243-year history. And with many Republican senators vowing to withhold judgment, that confidence may fade if the president faces a trial in the Senate early next year.
Despite claims by the Republicans to the contrary, there is already a mountain of evidence against the president: The reconstructed transcript of a call suggests Mr. Trump pressed his Ukrainian counterpart to begin politically beneficial investigations into the Bidens and an unsubstantiated theory of Democratic collusion in 2016, and thousands of pages of testimony document efforts to hold up military aid and a White House meeting unless Ukraine announced investigations into Mr. Trump’s political rivals.
Much of that testimony has centered on the actions of Rudolph W. Giuliani, the president’s personal lawyer, and a handful of Trump loyalists like the ambassador to the European Union, Gordon D. Sondland, who tried to manage Ukraine policy outside the normal diplomatic channels.
Democrats promise that the public hearings, which begin Wednesday with William B. Taylor Jr., the top American diplomat in Ukraine, will methodically connect those actions to Mr. Trump and lay out the case that he abused the levers of his power for personal political advantage. In recent days, Adam B. Schiff, Democrat of California and the chairman of the House Intelligence Committee, said the public would “learn firsthand about the facts of the president’s misconduct.”
But after stumbling for weeks toward a coherent response, several people familiar with Republican deliberations said lawmakers were being hypervigilant about guarding against even the hint of a defection in their ranks. Any suggestion of support for impeachment could cause the dam to break, inflicting political damage on them and Mr. Trump, they fear.
The president’s defenders said they planned to do everything they could to sow doubt about the substance of the impeachment allegations, while trying to avoid the temptation to question the motivations and backgrounds of the witnesses called by Democrats — an approach they believe could backfire. They will leave that to Mr. Trump, who has regularly attacked witnesses on Twitter and in rants to reporters. On Friday, he denigrated the testimony as false and accused the witnesses of being “Never Trumpers” who “hate President Trump.”
Republicans acknowledge that they may not be able to stop Democrats from muscling through articles of impeachment on a party-line basis, but the party leaders believe they can stave off defections in the House and help ensure a speedy acquittal in the Republican-controlled Senate.
They will be helped by the fact that the burden is on the Democrats to make their case for removing Mr. Trump a year before a presidential election, said Ross H. Garber, one of the nation’s leading impeachment lawyers.
“The Democrats are trying to build a very high Jenga tower and Republicans just have to pull out a couple key pieces and the whole thing comes toppling down,” Mr. Garber said, referring to the popular game of carefully balanced wooden blocks.
Representative Devin Nunes of California, the top Republican on the House Intelligence Committee, is still expected to take the lead in outlining the Republicans’ case. But on Friday, Republicans temporarily moved Representative Jim Jordan of Ohio, one of their fiercest questioners, to the committee so that he could participate in grilling the witnesses.
The list of witnesses requested by Republicans includes Hunter Biden, the former vice president’s younger son; Alexandra Chalupa, who worked at the Democratic National Committee during the 2016 campaign; Nellie Ohr, who worked with Fusion GPS, an opposition research firm that assembled a dossier of allegations about Mr. Trump and Russia; and Devon Archer, a board member at Burisma Holdings, the Ukrainian company where Mr. Biden was also a board member.
The requests suggest Republicans are prepared to argue that Mr. Trump’s interest in those figures — and the pressure he put on Ukraine to investigate them — was legitimate.
Mr. Schiff responded Saturday to the witness requests, vowing that he would not let the hearings serve “as a vehicle to undertake the same sham investigations into the Bidens or 2016 that the president pressed Ukraine to conduct for his personal political benefit.” Under rules adopted by the House, Democrats have the final say on who is called to testify.
Republicans have also demanded testimony from the whistle-blower who revealed the existence of Mr. Trump’s July call with Volodymyr Zelensky, the president of Ukraine, and several foreign policy officials, like Kurt D. Volker, the former American special envoy to Ukraine, who they believe could paint Mr. Trump’s actions in a more favorable light.
In a letter to Mr. Schiff, Mr. Nunes anticipated a rejection from Mr. Schiff, writing that “your failure to fulfill minority witness requests shall constitute evidence of your denial of fundamental fairness and due process.”
Evidence of the emerging Republican approach was on display this week in transcripts of the impeachment testimony delivered by the stream of diplomats and national security officials in a secure hearing room in the Capitol basement.
They indicated that Republicans would portray figures like Mr. Giuliani as working in his own interests, not at Mr. Trump’s behest; and that they would argue that Mr. Sondland, a political megadonor with little diplomatic experience, was a braggart who exaggerated his relationship with Mr. Trump and essentially freelanced on his behalf.
The heart of that effort is the argument that few if any of the witnesses directly heard the president call for a quid pro quo. After Mr. Taylor testified about a September phone call in which he learned that the president wanted Ukraine to investigate his political rivals, Representative Lee Zeldin, Republican of New York, pounced.
“This isn’t firsthand. It’s not secondhand. It’s not thirdhand,” Mr. Zeldin said incredulously as he described a game of telephone among Mr. Taylor; Timothy Morrison, a top Russia and Europe expert on the National Security Council; Mr. Sondland; and Mr. Trump about Mr. Zelensky.
“You’re telling us that Tim Morrison told you that Ambassador Sondland told him that the President told Ambassador Sondland that Zelensky would have to open an investigation into Biden?” Mr. Zeldin asked Mr. Taylor.
“That’s correct,” Mr. Taylor responded.