The Trump Lawyer Who Wields Outsize Influence on the Next White House

President-elect Donald J. Trump was flying to Washington for his first face-to-face meeting with President Biden since winning the election when a top aide offered a startling idea to broker peace between Russia and Ukraine.

The adviser, Boris Epshteyn, who coordinated the legal defenses in Mr. Trump's criminal cases, suggested to the president-elect that he should be Mr. Trump's special envoy for the Russia-Ukraine conflict, according to four people briefed on what took place.

Mr. Epshteyn, who was born in Russia and lived there until he was 7, has no experience in foreign policy. He told the group that he had family on both sides of the conflict.

Several people on the plane appeared shocked at the idea of appointing Mr. Epshteyn to a sensitive diplomatic post, according to the people briefed on the matter. In addition to his lack of diplomatic experience, he is currently under indictment in Arizona along with several other Trump allies for their efforts to overturn the 2020 election with so-called fake electors. (A fifth person with knowledge of the events insisted people on the plane reacted well to the idea and suggested thoughts on how to structure such a move.)

But none of the people with knowledge of the incident disputed one key fact: The person on the plane who registered the least shock at the special envoy notion was the only person whose opinion ultimately matters. Mr. Trump listened with apparent interest and did not dismiss the proposal, even though he did not commit to it.

Whatever comes of Mr. Epshteyn's idea, Mr. Trump has already given his adviser extraordinary power and shown a willingness to heed his counsel above that of others. Even the world's richest man, Elon Musk, who has been in many transition meetings in the past week, has privately remarked at how surprised he is that Mr. Epshteyn has been granted so much authority.

The people who spoke for this were granted anonymity to discuss private deliberations. Mr. Epshteyn declined to comment, and a Trump spokesman did not respond to an email seeking comment.

Mr. Epshteyn, who left his role in the White House communications office in 2017 over what was described as an issue with his security clearance that has since been resolved, had told friends before the special envoy discussion that he intended to stay outside government as a counselor to Mr. Trump. And in Mr. Trump's world, the lack of an official title has meant little in terms of measuring influence.

In rapid-fire succession over two days this week, Mr. Epshteyn assembled for Mr. Trump the Justice Department staffing he always wanted and felt he never got in his first term. Mr. Trump, who has never respected the post-Watergate norm that the department should operate with independence, has a team stacked with loyal fighters and three of his personal lawyers.

Mr. Epshteyn, a physically imposing man who wears three-piece suits, has flexed his power in other ways as well.

While the incoming White House chief of staff, Susie Wiles, was traveling to and from a conference featuring some of Mr. Trump's donors over the weekend and on Monday, Mr. Epshteyn finalized a push for Mr. Trump's eventual pick for White House counsel, William McGinley, according to two people briefed on the matter.

And he ran one of his most audacious plays yet this week. He was a key behind-the-scenes advocate for Mr. Trump's decision to announce Representative Matt Gaetz of Florida as his choice for attorney general. Mr. Epshteyn made his case aboard the round-trip flights on Mr. Trump's airplane from West Palm Beach, Fla., to Washington on Wednesday, according to two people with knowledge of what happened.

Mr. Epshteyn had argued for other choices before that, including the lawyer Robert Giuffra. But when Mr. Gaetz, who himself has been investigated by the Justice Department, emerged as an option, he pushed heavily for it, according to two of the people briefed on what took place.

Mr. Epshteyn is licensed to practice law in New York, although he did not renew his attorney registration within 30 days of his birthday in August this year as required by the Office of Court Administration, according to the office's website. That meant a roughly two-month period in which he was not in compliance with state requirements; the court system typically grants grace periods and provides warnings before taking any form of disciplinary action.

After being contacted late Thursday for comment about the registration for this , Mr. Epshteyn appears to have filed the required renewal.

Over the years, Mr. Epshteyn has called for an aggressive legal strategy for his boss. He was among the lawyers who encouraged Mr. Trump to delay his trials as long as possible, kicking them close to or beyond the election so that they would be politically impractical.

That strategy was difficult and expensive — the costs were paid by a political action committee Mr. Trump created in 2021, and it involved swamping the system with legal briefs. But it was ultimately successful in keeping Mr. Trump from being sentenced in the one criminal trial that did take place.

Whatever title Mr. Epshteyn is eventually given — whether it is "counselor" or "adviser" or something else — his influence inside government is built to last.

The key legal posts that Mr. Trump has announced so far for his second administration look remarkably similar to a list of suggested names for top administration lawyers that was compiled by some Trump advisers outside the formal transition process with input from Mr. Epshteyn. The list was obtained by The New York Times.

Mr. Epshteyn also helped influence a proposal, captured in a memo that circulated at the top levels of Mr. Trump's orbit, calling for using private investigators for background checks on incoming staff members, bypassing the traditional F.B.I. process, and then having the president-elect summarily grant most of them security clearances as soon as he takes office.

Officials have not said what their plan is for clearances, but several Trump advisers said they anticipated Mr. Trump availing himself of what was proposed for him to do.

One Trump adviser, who asked not to be identified for fear of retaliation from Mr. Epshteyn, described the overall situation as "the United States of Boris."