It is not easy to explain why the president won’t concede the Russia question, but aides and friends say the matter hits him where he is most vulnerable. Mr. Trump, who often conflates himself with the institutions he serves, sees questions about Russia as an effort by Democrats and stragglers from the “Never Trump” movement to delegitimize his election victory.

There is another reason, too. Mr. Trump is a wealthy businessman from New York, but he is not a Wall Street titan or a master investor. He is a real estate mogul whose life view is predicated on making deals and who treats almost everything as an open-ended discussion. When it comes to where he stands on Russia and the 2016 election, Mr. Trump, in keeping with his signature approach to almost every issue, appears to be leaving his options open.

It was a winning formula during the campaign. Mr. Trump talked in generalities, refusing to commit to specific policy proposals. “We’re going to have to look at a lot of things very closely,” was a frequent, vague refrain.

He would speak supportively of both sides of an issue, sometimes in the same sentence, forcing interviewers to scramble to pin him down and leaving supporters and detractors reading what they chose into his words.

“President Trump treats every issue like an ongoing negotiation by hedging his comments with phrases that allow a flexible interpretation of his position,” said Ryan Williams, a Republican strategist and a former aide to Mitt Romney. “He refuses to get backed into a corner or pinned down on a specific position so that he always has the option of changing his mind and making a course correction in the future.”

His aides have mirrored that strategy.

On Friday, when Sean Spicer, the White House press secretary, was asked by a reporter if the president stood by his lone January statement that Russia was behind the email hacking, Mr. Spicer replied vaguely: “Of course. He’s concerned about any country or any actor that wants to interfere in elections.”

But the campaign is long over. While many of Mr. Trump’s allies and supporters are still reluctant to blame Russia, the American intelligence community has said that Russian interference is a fact, not an opinion. Mr. Trump’s strategy of muddying his position has let the Russia issue grow, gumming up the gears in his administration’s efforts to move forward with major legislation and decisions.