President Trump speaks to reporters on his way to board Marine One from the South Lawn of the White House on Friday. (Mandel Ngan/AFP/Getty Images)

President Trump is waging a war of attrition against special counsel Robert S. Mueller III’s investigation. If his goal is to poison the reception to whatever Mueller’s findings turn out to be, as seems evident from what he and his allies have done, he is making progress.

The slow but steady separation of public opinion underscores the degree of success in the president’s strategy. Through constant tweets in which he has used exaggeration, distortion and outright falsehoods — combined with the activities of his congressional supporters in hectoring the Justice Department and the FBI — Trump hopes to turn the ultimate confrontation into one more partisan battle.

He has created diversions that have helped to reshape attitudes, primarily among Republicans. It started long ago, when he charged, without evidence, that President Barack Obama had wiretapped the phones in Trump Tower during the 2016 campaign. That proved to be false, but it did not deter him from claiming other alleged abuses without solid evidence to back them up.

The latest is what he labels “Spygate,” the claim that the Obama administration planted a spy inside the Trump campaign. As always, this involves some clever — and cynical — branding by a president who is a master of the game.

The available evidence says something to the contrary, which was that FBI officials were concerned enough about Russian interference in the election and about contacts between Russians and several people involved in the Trump campaign that they used a confidential source to talk with Trump associates. If Trump is suggesting that the goal of this was to somehow disrupt the Trump campaign or deny him the presidency, it was an utter failure. But that was not the goal, based on everything in public view.

The president has used this claim to insert himself into the investigation in ways that break the norms. His tweets forced Deputy Attorney General Rod J. Rosenstein to ask for an inspector general’s investigation into the matter. Meanwhile, congressional Republicans, led by Rep. Devin Nunes (R-Calif.), demanded to see relevant DOJ documents.

That resulted in two meetings on Thursday that were carried out amid partisan bickering and controversy over whether Democrats would be allowed to attend. In the end, Democrats were allowed in, though that did nothing to resolve underlying differences. Meanwhile, nothing was revealed to buttress Trump’s claims.

Among those who showed up for the meetings were White House Chief of Staff John F. Kelly, and the newly hired White House lawyer tasked with handling the Mueller investigation, Emmet T. Flood. Their attendance, given that the discussions involved an ongoing investigation involving the Trump campaign, created another controversy. White House officials insisted they were there only briefly and to relay a message from the president calling for transparency.

The pattern continues to repeat itself. Step by step, week by week, the president and his allies cross lines that legal experts insist should not be crossed. The president’s ongoing conflict with the Justice Department and his inflammatory tweets about the Mueller investigation have become so commonplace that it can be easy for people to forget how abnormal it all is.

Sen. Jeff Flake (R-Ariz.) noted this Wednesday in his commencement address to graduates of Harvard Law School. Speaking about Trump’s demand for an investigation into the use of the confidential source and the claim that it involved spying, Flake said, “I pick this egregious example of recent presidential conduct not because it is rare in terms of this president’s body of work, but because it so perfectly represents what we have tragically grown accustomed to in the past year and a half.”

Trump’s efforts have moved public opinion in ways that must cheer the president. Over time, there has been an erosion in support for the Mueller investigation among Republicans. This partisan division will shape the environment whenever Mueller concludes his investigation and particularly if he delivers a report highly critical of the president.

A CNN poll taken earlier this month found a slight shift against Mueller among all Americans, with 44 percent approving of his handling of the investigation and 38 percent disapproving. That approval slipped from the 48 percent who approved two months earlier. But among Republicans, approval dropped from 29 percent in March to just 17 percent in May.

A Quinnipiac University survey taken in April found that 61 percent of Republicans said that the Mueller investigation is unfair, while just 26 percent said it is fair. Early this year, there was closer to an even split among Republicans in their assessment of the investigation, with 46 percent saying then it was not fair.

A Quinnipiac poll conducted earlier in the year found Republican assessments of the FBI turning more negative. In January, Republicans were evenly split — 40 percent and 40 percent — on whether they approved or disapproved of the bureau’s work. By February, Republicans who approved had dropped to 28 percent, and those who disapproved had risen to 53 percent.

Those shifts in opinion reflect both the degree to which Trump has taken over the Republican Party and the degree to which there has been little pushback from GOP congressional leaders when he has crossed the lines. While these leaders say they support the Mueller investigation, they have resisted calls for legislation that would offer protections.

Meanwhile, House Speaker Paul D. Ryan (R-Wis.) has done nothing visible to rein in Nunes. In recent forums, Ryan has decried “moral relativism” and “tribalism” that he said now infect America’s politics. The tribalism predated Trump’s election, but the president’s conduct has made this problem worse. Ryan made no mention of the president’s behavior in the context of those remarks.

Flake, however, leveled criticism at both the president and Congress in his commencement speech. The presidency, he said, has been “debased by a figure who has a seemingly bottomless appetite for destruction and division.” At the same time, he said, “Congress is utterly supine in the face of the moral vandalism that flows from the White House daily.”

The gap between the Jeff Flakes of the Republican Party and what increasingly is a pro-Trump majority among rank-and-file Republican voters underscores how successful the president has been in shaping opinion ahead of whatever judgment is leveled by the special counsel and his team. Trump’s strategy of confrontation probably will only intensify in the weeks or months ahead.