He won't compartmentalize. With aides, advisers and friends breezing in and out of the Oval Office, it is not uncommon for the president to suddenly turn the conversation to Russia — a subject that perpetually gnaws at him — in a meeting about something else entirely.
And he won't discipline himself. Trump's legal team, led by Marc E. Kasowitz of New York, is laboring to underscore the potential risk to the president if he engages without a lawyer in discussions with other people under scrutiny in widening Russia inquiries, including Jared Kushner, his son-in-law and senior adviser.
Nearly two months after Trump retained outside counsel to represent him in the investigations of alleged Russian meddling in last year's election, his and Kushner's attorneys are struggling to enforce traditional legal boundaries to protect their clients, according to half a dozen people with knowledge of the internal dynamics and ongoing interactions, who spoke on the condition of anonymity to discuss the matter candidly.
Compounding the challenges have been tensions between Trump's and Kushner's legal teams in a frenzied, siege-like environment. Senior White House officials are increasingly reluctant to discuss the issue internally or publicly and worry about overhearing sensitive conversations, for fear of legal exposure.
"Stuff is moving fast and furious," said one person familiar with the work of the legal teams. "The tensions are just the tensions that would normally exist between two groups of lawyers starting to work together and struggling with facts that we don't all know yet."
A third faction could complicate the dynamic further. Trump's eldest child, Donald Trump Jr., hired his own criminal defense attorney this week amid disclosures that he met with a Russian lawyer with ties to the Kremlin who he thought could provide incriminating information about Democrat Hillary Clinton during the campaign. Trump Jr. also is considering hiring his own outside public relations team.
In remarks to reporters on Air Force One before his arrival in Paris on Thursday, Trump defended his son as "a good boy" who had done nothing wrong and suggested he would support Trump Jr. testifying about the case "if he wants to."
As in Trump's West Wing, lawyers on the outside teams have been deeply distrustful of one another and suspicious of motivations. They also are engaged in a circular firing squad of private speculation about who may have disclosed information about Trump Jr.'s meeting with the Russian lawyer to the New York Times, said people familiar with the situation.
Michael J. Bowe, a partner at Kasowitz's firm and a member of Trump's legal team, said the lawyers are collaborating effectively. "The legal teams have worked together smoothly and professionally from the start," he said.
Another question is who will pay the legal fees for the president and administration officials involved in the Russia inquiries. Some in Trump's orbit are pushing the Republican National Committee to bear the costs, said three people with knowledge of the situation, including one who euphemistically described the debate as a "robust discussion."
Although the RNC does have a legal defense fund, it well predates the Russia investigations and is intended to be used for legal challenges facing the Republican Party, such as a potential election recount.
The RNC has not made a decision, in part because the committee is still researching whether the money could legally be used to help pay legal costs related to Russia. But many within the organization are resisting the effort, thinking it would be more appropriate to create a separate legal defense fund for the case.
RNC officials declined requests for comment. The White House has not said whether Trump, Kushner and other officials are paying their legal bills themselves or whether they are being covered by an outside entity.
Those retained by the parties involved include Kasowitz, Bowe and Jay Sekulow for Trump; Jamie S. Gorelick and Abbe Lowell for Kushner; and Alan Futerfas for Trump Jr.
The president has been irritated with Kasowitz, which the Times first reported this week. The two men have known each other for decades, and both are hard-charging, prideful and brash.
But people briefed on the evolving relationship said Trump has made Kasowitz absorb his fury about the Russia inquiries — in keeping with how the president treats his White House staff, quick to blame aides when things go awry.
The lawyers are now faced with the challenge of trying to force change on Trump, 71, who throughout his life has often thrived amid freewheeling chaos. He made his name as a flamboyant Manhattan developer, trafficking in hyperbole and mistruth — or "puffery," as one former aide put it — while exhibiting little discretion in his daily conversations. For Trump, this was a formula for success.
"There's no question that Donald Trump has lied flagrantly and almost pathologically his entire life," said Timothy L. O'Brien, author of the Trump biography "TrumpNation" and a Bloomberg View columnist. "For good parts of his life, he's been insulated from the consequences of doing that."
Trump is now the highest elected official in the nation, and with that outsize perch comes potentially outsize consequences. His legal team is trying to impress upon him and those in his orbit that there could be severe ramifications for lying to federal investigators or congressional committees.
O'Brien said, "He is now in a completely different world, and it's a world unlike any he's ever existed in before — both in terms of the sophistication and honesty that's required of him to do his job well, and most especially the titanic legal and reputational consequences of Donald Trump continuing to be the same old Donald Trump."
The president, however, believes he has done nothing wrong and is the target of what he repeatedly has called "a witch hunt." His instinct, those close to him have said, is to trust his gut and punch back.
Barry Bennett, who was a Trump campaign adviser, said that Trump isn't used to losing and that "he never stops fighting. That's what life has taught him."
During last year's campaign, Bennett recalled, "do you know how many times people came to him and said, 'That was lethal, you're never going to survive it'? Every time, he survived. When somebody tells him he can't do something, he's at a minimum circumspect."
When it comes to Twitter, however, the president is hardly circumspect. His political advisers have long urged him to restrain his first impulses on social media and to think twice before tweeting — and now, his lawyers are asking the same.
Still, the president persists.
"It's my voice,'' Trump said in a recent interview with the New York Times Magazine. ''They want to take away my voice. They're not going to take away my social media.''
Robert Costa, Rosalind S. Helderman and Carol D. Leonnig contributed to this report.