The White House has enlisted two dozen attorneys, legislative liaisons and others to craft strategies in the face of Republican threats to charge the president with high crimes and misdemeanors.Just before 8 p.m. on Thursday, Representative Marjorie Taylor Greene posted a video of herself at a town hall in her Georgia district declaring that she “will not vote to fund the government” unless the House holds a vote to open an impeachment inquiry against President Biden.It took just 68 minutes for the White House to fire back with a blistering statement that such a vote would mean that House Republicans had “caved to the hard-core fringe of their party in prioritizing a baseless impeachment stunt over high-stakes needs Americans care about deeply” like drug enforcement and disaster relief.The White House, as it turns out, is not waiting for a formal inquiry to wage war against impeachment. With a team of two dozen attorneys, legislative liaisons, communications specialists and others, the president has begun moving to counter any effort to charge him with high crimes and misdemeanors with a best-defense-is-a-good-offense campaign aimed at dividing Republicans and taking his case to the public.The president’s team has been mapping out messaging, legal and parliamentary strategies for different scenarios. Officials have been reading books about past impeachments, studying law journal articles and pulling up old court decisions. They have even dug out correspondence between previous presidential advisers and congressional investigators to determine what standards and precedents have been established.At the same time, recognizing that any impeachment fight would be a political showdown heading into an election season, outside allies have been going after Republicans like Ms. Greene and Speaker Kevin McCarthy. A group called the Congressional Integrity Project has been collecting polling data, blitzing out statements, fact sheets and memos and producing ads targeting 18 House Republicans representing districts that voted for Mr. Biden in 2020.“As the Republicans ramp up their impeachment efforts, they’re certainly making this a political exercise and we’re responding in kind,” said Kyle Herrig, the executive director of the Congressional Integrity Project. “This is a moment of offense for Democrats. They have no basis for impeachment. They have no evidence. They have nothing.”The White House preparations do not indicate that Mr. Biden’s advisers believe an impeachment inquiry is inevitable. But advisers who spoke on condition of anonymity to describe internal thinking said that it was important to take on the prospect aggressively and expressed hope that the situation could be turned to their advantage.Republican congressional investigations have turned up evidence that Hunter Biden traded on his family name to generate multimillion-dollar deals and a former partner, Devon Archer, testified that Mr. Biden would put his father on speakerphone with potential business clients to impress them.Republican congressional investigations have turned up evidence that Hunter Biden traded on his family name to generate multimillion-dollar deals.Doug Mills/The New York TimesBut Mr. Archer testified that the elder Biden only engaged in idle chitchat during such calls, not business, and no evidence has emerged that the president directly profited from his son’s deals or used his power inappropriately while vice president to benefit his son’s financial interests.Republicans have not identified any specific impeachable offenses and some have privately made clear they do not see any at the moment. The momentum toward an impeachment inquiry appears driven in large part by opposition to Mr. Biden’s policies and is fueled by former President Donald J. Trump, who is eager to tarnish his potential rival in next year’s election and openly frames the issue as a matter of revenge. “Either IMPEACH the BUM, or fade into OBLIVION,” he demanded of Republicans on his social media site this past week. “THEY DID IT TO US!”That stands in sharp contrast to other modern impeachment efforts. When impeachment inquiries were initiated against Presidents Richard M. Nixon, Bill Clinton and Mr. Trump, there were clear allegations of specific misconduct, whether or not they necessarily warranted removal from office. In Mr. Biden’s case, it is not clear what actions he has taken that would be defined as a high crime or misdemeanor.Mr. McCarthy, the California Republican, cited “a culture of corruption” within the Biden family in explaining on Fox News last weekend why he might push ahead with an impeachment inquiry. “If you look at all the information we’ve been able to gather so far, it is a natural step forward that you would have to go to an impeachment inquiry,” he said.Even if Republican investigators turned up evidence that Mr. Biden had done something as vice president to help his son’s business, it would be the first time a president was targeted for impeachment for actions taken before he became president, raising novel constitutional issues.For now, though, it is hardly certain that Republicans would authorize an inquiry. Mr. McCarthy told Breitbart News on Friday that if they pursued such an inquiry, “it would occur through a vote on the floor,” not through a decree by him, and veteran strategists in both parties doubt he could muster the 218 votes needed to proceed.The speaker’s flirtation with holding such a vote may be simply a way of catering to Ms. Greene and others on his right flank. He has used the thirst to investigate Mr. Biden as an argument against a government shutdown, suggesting that a budgetary impasse would stall House inquiries.Representative Marjorie Taylor Greene has vowed to oppose funding the government unless the House holds a vote to open an impeachment inquiry against President Biden.Kenny Holston/The New York TimesBut some Republicans have warned that a formal impeachment drive could be a mistake. Representative Ken Buck, Republican of Colorado, has said that “impeachment theater” was a distraction from spending issues and that it was not “responsible for us to talk about impeachment.” Ari Fleischer, a former White House press secretary under President George W. Bush, said impeachment could “unleash an internal Republican civil war” and if unsuccessful lead to “the worst, biggest backfire for Republicans.”The White House has been building its team to defend against Republican congressional investigations for more than a year, a team now bracing for a possible impeachment inquiry. Richard Sauber, a former federal prosecutor, was appointed special counsel in the spring of last year, and Ian Sams, a longtime Democratic communications specialist, was brought on as spokesman for the White House Counsel’s Office. Russell Anello, the top Democratic staff member for the House Oversight Committee, joined last year as well.After Republicans won control of the House in the November midterm elections, more people were added to handle the multitude of congressional investigations. Stuart Delery, the White House counsel who is stepping down this month, will be replaced by Ed Siskel, who handled Republican investigations into issues like the Benghazi terror attack for President Barack Obama’s White House.A critical adviser for Mr. Biden will be his personal attorney, Bob Bauer, one of the most veteran figures in Washington’s legal-political wars. As a private lawyer, he advised the House Democratic leader during Mr. Clinton’s impeachment and then the Senate Democratic leader during the subsequent trial, helping to shape strategies that kept Democrats largely unified behind their president.Mr. Biden himself has seen four impeachment efforts up close during his long career in Washington. He was a first-term senator when Mr. Nixon resigned rather than face a seemingly certain Senate trial in 1974 and a fifth-term senator when he voted to acquit Mr. Clinton in 1999. It was Mr. Biden that Mr. Trump tried to strong-arm Ukraine into investigating, leading to the former president’s first impeachment in 2019. And it was Mr. Biden’s victory in 2020 that Mr. Trump tried to overturn with the help of a mob that attacked Congress on Jan. 6, 2021, leading to a second impeachment.The Clinton impeachment battle has provided some lessons for the Biden team, although the circumstances are significantly different and the political environment has shifted dramatically in the 25 years since then. Much as the Clinton White House did, the Biden White House has tried to separate its defense against Republican investigators from the day-to-day operations of the building, assigning Mr. Sams to respond mostly off camera to issues arising from the investigations rather than Karine Jean-Pierre, the White House press secretary, during her televised briefings.As in the late 1990s, the strategy now is to paint Republicans as rabid partisans only interested in attacking the president of the other party out of political or ideological motives in contrast to a commander in chief focused on issues of importance to everyday voters, like health care and the economy.The approach worked for Mr. Clinton, whose approval ratings shot up to their highest levels of his two terms, surpassing 70 percent, when he was impeached for perjury and obstruction of justice. Mr. Biden’s approval ratings remain mired in the low 40s, but advisers think a serious impeachment threat would rally disaffected supporters.Mr. Herrig’s Congressional Integrity Project, founded after last year’s midterm elections, hopes to turn the Republican impeachment drive against them. His group’s board chairman, Jeff Peck, is a longtime Biden ally, and it recently hired Kate Berner, the former White House deputy communications director.The group has teams in New York and California and plans to expand to other battleground districts. “This is a political loser for vulnerable Republicans,” Mr. Herrig said. “McCarthy’s doing the bidding of Trump and Marjorie Taylor Greene and putting his majority at risk.” More