“There is a reason for the old lawyer’s proverb — the fish got hooked because it opened its mouth,” said Robert F. Bauer, a White House counsel under President Barack Obama. “Tweeting spontaneous thoughts and feelings may be emotionally satisfying in the middle of the night, but Mr. Trump’s lawyers will surely remind him that there are always fishermen around, casting their lines.”

More than ever before, the White House is looking at the Russia case through a legal prism and hoping to wall it off from day-to-day governance. The president’s aides are assembling a team of lawyers, including some who would join the staff and others who would remain outside the White House. Individual aides are also shopping for lawyers…

Every lawyer consulted by White House aides in recent days has made the same point about the president’s tweets: He can power through the investigations, but he is his own worst enemy if he continues to vent online. The lawyers noted that Mr. Trump’s words have already been used against him in court cases challenging his orders temporarily barring visitors from several predominantly Muslim countries. Judges cited his statements during the campaign as evidence of his motives.

Whether the same could be true in criminal proceedings was unclear, some lawyers said, but they asked why he would take the chance.