(CNN) Chief Justice John Roberts has watched, silently, as Donald Trump denigrated judges over the years, complaining about one because of his Mexican heritage, referring to another as a "so-called judge" when he ruled against the administration's Muslim travel ban.

As the episodes piled up, from Trump's campaign time in 2016 and into his presidency, the man who sits at the helm of the federal judiciary said nothing.

Not to mention a rejoinder three hours later from Trump on Twitter.

The startling series of events -- which showed a bolder side of Roberts -- demonstrated just how much Trump's relationship with the third branch has devolved. The US Judiciary has strived to be above the political fray that has only been exacerbated by Trump.

Roberts' response stems specifically from Trump's comments on Tuesday on District Court Judge Jon Tigar's Monday night decision to temporarily block an executive order that would have scaled back US asylum policy. Trump criticized the San Francisco-based Tigar, nominated in 2012, as an "Obama judge." Of the regional US circuit court that would oversee any appeal of the case, Trump declared, "an automatic loss" for the administration and "the 9th Circuit is very unfair."

In a statement on Wednesday, made public because of a query from The Associated Press, Roberts said, "We do not have Obama judges or Trump judges, Bush judges or Clinton judges. What we have is an extraordinary group of dedicated judges doing their level best to do equal right to those appearing before them. That independent judiciary is something we should all be thankful for."

It was not the first time Roberts had been asked to comment, but it was the first time he decided to go public. A 2005 appointee of Republican President George W. Bush, Roberts did not explain his timing.

But it may arise from the combination of Trump's specific insult -- portraying Tigar in a political realm based on the president who appointed him -- as well as the recent confirmation turmoil over new Supreme Court Justice Brett Kavanaugh

Roberts' public concern for the reputation of the federal judiciary comes as the Supreme Court is riven 5-4 along ideological and political lines. The recent retirement of swing vote Justice Anthony Kennedy has deepened the split, and Roberts has already signaled an effort to try to lessen the divisions among the nine.

The chief justice spoke out broadly about judicial independence in October after the tumultuous Kavanaugh hearings. Addressing a University of Minnesota audience, Roberts referred to "the contentious events in Washington of recent weeks" and then asserted the high court's independence from the executive and legislative branches.

"I will not criticize the political branches," he said. "We do that often enough in our opinions. But what I would like to do, briefly, is emphasize how the judicial branch is -- how it must be -- very different."

Roberts' statement on Wednesday was of a different magnitude, stronger and deliberately echoing back the President's own remark about an "Obama judge."

The chief justice has often expressed dismay when judges are referred to by political affiliation. He has also observed since 2010, with the retirement of liberal Justice John Paul Stevens, an appointee of Republican President Gerald Ford, that it may be more difficult to convince the public of justices' impartiality from politics.

Since Stevens was succeeded by Obama-appointee Elena Kagan, and continuing with Trump's choice of Kavanaugh, the court's five conservative justices were named by Republican presidents and the four liberals -- often relegated to the dissent -- were named by Democratic presidents.

With Kennedy's retirement, Roberts is now ideologically at the middle of the court, and he may be inclined to hedge his own conservative instincts to steady the bench and avoid more polarization.

As he considered whether to answer Trump's latest affront to the judiciary on Tuesday, Roberts no doubt weighed how much he might provoke Trump. Roberts plainly concluded it was time to defend judiciary's special role in America's democracy.

The 63-year-old chief was likely not surprised that within three hours, Trump fired back in two consecutive tweets: "Sorry Chief Justice John Roberts, but you do indeed have 'Obama judges,' and they have a much different point of view than the people who are charged with the safety of our country. It would be great if the 9th Circuit was indeed an 'independent judiciary,' but if it is ... are so many opposing view (on Border and Safety) cases filed there, and why are a vast number of those cases overturned. Please study the numbers, they are shocking. We need protection and security - these rulings are making our country unsafe! Very dangerous and unwise!"

Roberts offered no new retort. And given the chief justice's aversion to the appearance of politics, he is unlikely to offer any response any time soon.