President Trump arrived for a news conference with Colombian President Juan Manuel Santos at White House on May 18. (Andrew Harnik/AP)

A current, senior White House adviser — not merely another former campaign aide or distant associate of President Trump — has been identified by federal investigators as a significant person of interest in a probe aimed at determining whether Trump's political team colluded with Russia to meddle in the 2016 election.

Let that sink in.

Among many things, the focus on someone close to the president means that the firewall protecting him from the full heat of media scrutiny is crumbling. Though he complained this week that “no politician in history . . . has been treated worse or more unfairly,” the reality is that Trump has been somewhat insulated by journalists’ inability to show that the FBI investigation touches him or anyone on his White House staff directly.

Trump has insisted that he is not in the FBI’s crosshairs, claiming last week that the agency’s then-director, James B. Comey, told him on three occasions that he is not a target. And the White House has attempted to distance itself from known targets such as Paul Manafort, Roger Stone and Carter Page.

The law enforcement investigation into possible coordination between Russia and the Trump campaign has identified a current White House official as a significant person of interest. (The Washington Post)

At one point, White House press secretary Sean Spicer told reporters that Manafort, who chaired Trump’s campaign before being replaced by Kellyanne Conway, “played a very limited role for a very limited amount of time.”

Laughable as that assertion was, the press has felt obligated to exercise dual restraint: It is possible that any contacts between campaign officials and Russians were not part of a coordinated effort to collect and disseminate damaging information about Hillary Clinton. And it is possible that even if there was collusion, it happened without Trump’s knowledge.

Both possibilities are still, well, possible. But in the context of the FBI investigation, the separation between Trump and those working on his behalf is shrinking as the probe pushes nearer to his inner circle. Though it is too early to know what the FBI will conclude, the attention on someone Trump continues to lean on as president would appear to increase the likelihood that if collusion occurred, he might have been aware of it.

In the simplest terms, there is a big difference between headlines that say “one of the president’s senior advisers is under investigation” and headlines that say “some people who used to work for candidate Trump are under investigation.”

Trump now enters a new phase in which the focus of press coverage will sharpen. Many stories have been written about his failure to vet staffers more thoroughly. The New York Times reported Wednesday that Trump’s team knew Michael Flynn was the subject of a separate FBI investigation yet still named him national security adviser, making the president’s judgment all the more questionable.

It is getting harder and harder to give Trump the benefit of the doubt — to continue attributing his hiring of people who draw FBI scrutiny to innocent carelessness. Expect the White House to confront more aggressive inquiries about whether Trump knew what his staffers might have been up to.