On his last day as president on Jan. 20, 2021, Donald J. Trump stood in a snapping wind and waved goodbye to relatives and supporters before he took his final flight on Air Force One back to Mar-a-Lago. No elected Republican of any stature showed up at Joint Base Andrews for the bleak farewell.

Mr. Trump, at that moment, was a pariah among Republican elites. The party’s leaders in the House and Senate, Kevin McCarthy and Mitch McConnell, blamed him for the Capitol siege. Party fund-raisers assured donors they were done with him. On conference calls, House Republican leaders contemplated a “post-Trump” G.O.P.

Today, three years after Jan. 6 and more than a week before the Iowa caucuses, Mr. Trump has almost entirely subjugated the elected class of the Republican Party. As of this week, every member of the House Republican leadership is formally backing his campaign to recapture the White House.

Mr. Trump has obsessed over his scorecard of endorsers, according to more than half a dozen Trump advisers and people in regular contact with him, most of whom insisted on anonymity to describe private conversations.

He sees gathering the formal endorsements as a public validation of his triumphant return that serves his strategy of portraying himself as the inevitable victor. He calls endorsements the “E word”; when lawmakers merely say they “support” him, he considers it insufficient and calls that the “S word.” In recent weeks, his allies have told lawmakers that Mr. Trump will be closely watching who has and hasn’t endorsed him before the Iowa caucuses on Jan. 15.

Mr. Trump works his endorsements through both fear and favor, happily cajoling fellow politicians by phone while firing off ominous social media posts about those who don’t fall in line quickly enough. In October, he felled a top candidate for House speaker, Representative Tom Emmer, by posting that voting for him “would be a tragic mistake!” On Wednesday, Mr. Emmer capitulated and endorsed him.

“They always bend the knee,” Mr. Trump said privately of Mr. Emmer’s endorsement, according to a person who spoke to him.

And Mr. Trump is privately ranting about and workshopping nicknames for other holdouts, like Senator Ted Cruz of Texas.

“Ted — he shouldn’t even exist,” Mr. Trump said recently of Mr. Cruz, a 2016 rival, according to a person who heard the remarks and recounted them soon after. “I could’ve destroyed him. I kind of did destroy him in 2016, if you think about it. But then I let him live.”

Aided by a disciplined and methodical political operation and by the rallying effect that his criminal charges have had on Republicans, Mr. Trump has demonstrated a remarkable show of force for a former president whose impeachment on the way out of office was supported by more members of his own party than any previous impeachment in American history. And he has done this while facing 91 felony charges across four criminal cases.

Though he still brands himself an outsider, Mr. Trump is now unequivocally the favored candidate of Republican insiders. His rivals, Gov. Ron DeSantis of Florida and former Gov. Nikki Haley of South Carolina, are promoting their endorsements by the governors of the first two nominating states in Iowa and New Hampshire. Beyond that, the endorsements race, at the national level, has been a wipeout.

Mr. Trump has endorsements from nearly 100 members of the House of Representatives. The next closest candidate, Mr. DeSantis, who served in the House, has only five. Ms. Haley has one.

In the Senate — the body of elected Republicans most resistant to Mr. Trump — he has 19 endorsements. Mr. DeSantis and Ms. Haley have zero. More G.O.P. senators will soon follow. Senators John Barrasso and Cynthia Lummis of Wyoming are expected to endorse Mr. Trump before the Iowa caucuses, according to two people briefed on their thinking.

The chairmen of the Republican Party’s House and Senate campaign committees were both early endorsers of Mr. Trump. He has almost four times as many endorsements from governors as Mr. DeSantis has. Mr. Trump’s political team, meanwhile, has told people it plans to not work with the Republican Governors Association because the group’s executive director advises Gov. Kim Reynolds of Iowa, who endorsed Mr. DeSantis.

Mr. Trump has been courting Senator Tim Scott of South Carolina, placing several calls to him since he ended his campaign on Nov. 12 and deploying allies like Lindsey Graham, a fellow South Carolina senator, to make the case for Mr. Scott to issue an endorsement before their state’s primary on Feb. 24, two people familiar with the outreach said.

Mr. Trump has dealt with his 2024 campaign rivals differently from 2016 — with a longer view to gaining their endorsements.

In 2016, he derided nearly all of his competitors in deeply personal terms, mocking their physical appearances and even giving out the phone number of Mr. Graham, then a candidate, at a rally. In this campaign, Mr. Trump has saved his attacks for Mr. DeSantis and Ms. Haley, but has avoided criticizing others whose support he hopes to gain.

“People are looking around, ‘Hell, look at all these endorsements’ — that doesn’t happen overnight,” Mr. McCarthy, who announced his retirement from Congress after being driven out of the speakership, said in an interview. “He has a sophisticated system to going about it.”

Blunt force and threats

Early in his post-presidential life, Mr. Trump weaponized the power of his endorsement to an extent that no predecessor had ever attempted.

He made it known he was eager to intervene in Republican primaries. Given his cult following among G.O.P. voters, his endorsement, at times, packed the power to end a race.

Entire primary campaigns were organized around winning his endorsement. Trump insiders were hired by candidates as “consultants” for the sole purpose of saying nice things about them to Mr. Trump in the hope he might endorse them. Mr. Trump received these candidates at his homes in Florida and New Jersey and watched gleefully as they, in Mr. Trump’s own words to aides, “kissed my ass.”

In 2021, Mr. Trump endorsed dozens of candidates at every level. No chit was too small to collect, as when he endorsed Vito Fossella for borough president in Staten Island, N.Y. In the run-up to the 2022 midterm elections, Mr. Trump accelerated his efforts, ultimately endorsing more than 200 candidates.

Nowhere was his power more evident than in the Ohio and Pennsylvania Senate primaries. Mr. Trump endorsed J.D. Vance in Ohio and Mehmet Oz in Pennsylvania, taking two candidates not expected to win and ensuring their nominations. Mr. Oz lost in November, showing the limits of Mr. Trump’s sway in general elections. Mr. Vance became one of the first senators to endorse Mr. Trump and has been lobbying colleagues to do the same.

Republicans facing primaries saw that Mr. Trump could destroy their political careers. Then there were the 10 House Republicans who voted to impeach Mr. Trump in 2021. He sought revenge in 2022, and only two of the 10 are still in Congress.

Personal courtship

An underrated factor in Mr. Trump’s domination of party elites is his intense courtship of them — offering a level of direct access that no president in recent times has granted to rank-and-file lawmakers.

Since 2017, Mr. Trump has invested hundreds of hours in his political relationships, repeatedly using the trappings of the presidency to do so. He is constantly on the phone to Republican lawmakers. He invites them to dinner at his clubs, for rounds of golf and for flights on his jet.

His relationship-building paid huge dividends when he needed it most.

On Nov. 15, 2022, Mr. Trump announced his third campaign for president. The midterms had been horrible for Republicans and Mr. Trump received most of the blame. Trump-endorsed election deniers lost winnable races. The much-hyped “red tsunami” never materialized. Democrats defied expectations to hold onto power in the Senate. And Republicans, favored to seize the House by a big margin, won only the barest majority.

Making matters worse for Mr. Trump, the Republican who had the best night was his expected top rival in the 2024 primaries, Mr. DeSantis, who was re-elected in Florida in a landslide.

Only a handful of Mr. Trump’s most loyal supporters endorsed him right away. But Mr. Trump knew he had more support than was publicly evident. His team structured its early campaign activity around gathering endorsements, with Brian Jack, his former White House political director, who serves as his liaison to Congress, managing the process.

Last January, Mr. Trump traveled to the South Carolina Capitol for his first public campaign event, where he announced his leadership team in the state, led by Gov. Henry McMaster and Mr. Graham. This was a display of power in the backyard of his future 2024 competitors — Ms. Haley, the state’s former governor, and Mr. Scott, its junior senator.

Mr. Trump and his team replicated this approach in state after state — and by the early spring of 2023 they had momentum. The most important moment in the endorsement battle, according to Trump advisers, was his humiliation of Mr. DeSantis in Florida. As Mr. DeSantis took a heavily publicized trip to Washington in April, a month before he declared his candidacy, the Trump team ruined his visit by rolling out a series of congressional endorsements, including in Florida.

On April 20, Mr. Trump invited to dinner at Mar-a-Lago the 10 Florida lawmakers who had endorsed him. They arrived to signed Make America Great Again hats on their place settings. Representative Byron Donalds, a close DeSantis ally in the past, sat directly next to Mr. Trump.

A permission structure

The Trump team has focused on creating permission structures for Republican lawmakers queasy about Mr. Trump to feel comfortable again supporting him.

Senator Steve Daines of Montana, the chairman of the National Republican Senatorial Committee, the Republican Senate campaign arm, has been one of the most important players in that strategy.

In early February, Mr. Daines had his first face-to-face meeting with the former president after being elected to serve as chairman. They met in Mr. Trump’s office at Mar-a-Lago and Mr. Daines walked him through the Senate electoral map for 2024.

“It’s very important that the president and myself work closely not only on his re-election, but also, importantly, what we can do here to win back the United States Senate,” Mr. Daines said in an interview.

Mr. Daines did not endorse Mr. Trump that day. Instead, the chairman and Mr. Trump conveyed a powerful image to the rest of the party: They posed for a photograph, thumbs up, amid the familiar Mar-a-Lago décor of golden drapes and upholstery.

Less than three months later, in late April, Mr. Daines became the first member of the Republican Senate leadership to endorse Mr. Trump.