Nick Ayers, left, chief of staff to  Vice President Pence, and White House Chief of Staff John F. Kelly at a Cabinet meeting at the White House in May. (Jonathan Ernst/Reuters)

President Trump announced last Friday that his second White House chief of staff, retired Marine Corps general John Kelly, would be leaving that job soon. In his comments, Trump praised Kelly as “a great guy.” But for many months, there have been reports of mounting tension between the two; recently CNN reported that they were no longer speaking.

What will Kelly’s departure mean to the trajectory of the Trump White House? Well, let’s turn to the familiar joke:

Q: How many psychiatrists does it take to change a lightbulb?

A: Just one, but that lightbulb really has to want to change.

(Rimshot!)

Rep. Mark Meadows (R-N.C.) appears to be lobbying for the job, but others have shown a distinct lack of enthusiasm. Presumed heir Nick Ayers, chief of staff to Vice President Pence, took himself out of the running  Sunday.

But changing the chief of staff only matters if the president wants it to. And there is no sign from  Trump that he believes any change is needed. He has always seen himself as his only chief of staff — and after all, in his view, his presidency has already “accomplished more than any other U.S. administration in its first two (not even) years of existence.”

In the past, other presidents also tried to serve as their own chiefs of staff. This became known as the “spokes of the wheel” system, with the president at the hub and staffers, arrayed around the rim, reporting directly to him. But by the mid-1960s, growth in government generally had spurred corresponding growth in the White House. Where in 1939 the president had just six administrative assistants, the Johnson and Nixon staffs numbered in the hundreds. Bradley Patterson’s 2010 book on presidential staffers found them housed in 135 separate organizations, from the Office of Policy Development to the White House Medical Unit.

Given that, journalist Chris Whipple writes that those who sought to run the show themselves found “the result was chaos and confusion.” For instance, Gerald Ford, trying to contrast himself with Nixon, tried to reject Nixon’s reliance on a strong chief of staff. But he reversed himself. By the end of Ford’s term, that COS was Richard B. Cheney — who left behind a souvenir for the incoming Carter administration: a mangled bicycle wheel, with a note reading, “Beware the spokes of the wheel.”

Carter didn’t heed this advice. That was a “fatal mistake,” his aide Jack Watson would later note: “[I]t pulls the president into too much; he’s involved in too many things.” By 1979, Carter too had reorganized around an empowered chief of staff. “Empowered” mattered here: Bill Clinton’s first staff chief, Thomas “Mack the Nice” McLarty, could not rein in the president’s discursive decision-making habits. In 1993 he was replaced by the far stricter Leon Panetta.

All these hard-won lessons converged into what political scientists Karen Hult and Charles Walcott term “the standard model” of White House staffing. That model places a strong chief of staff atop an organizational hierarchy to meet “the evident need for systematic coordination and supervision in the institutional presidency,” managing “orderly flows of information that include the perspectives of and debates among relevant actors.” Reagan and Bush COS James Baker III argued that “the chief of staff has to ensure that the president hears all sides of an issue.”

The Trump transition team, it is safe to say, did not read the key back issues of Presidential Studies Quarterly. In the first days of the Trump White House, all spokes ran directly to the president; in July 2017, Kelly was brought in as a “beacon of discipline,” someone who could close the door to the Oval Office, most notably to Ivanka Trump and Jared Kushner. Using his military experience and gravitas, Kelly did have some early success in controlling the flow of people and paper to the president. Bob Woodward’s book “Fear” traces attempts by Kelly and staff secretary Rob Porter to provide “organized briefing papers with relevant information, different viewpoints, costs/benefits, pros and cons and consequences of a decision,” with the goal of ensuring that decisions were made systematically and delivered in signed presidential memorandums that had been cleared by everyone with responsibility for the subject area.

But this, as Woodward sums up, “was a fantasy.” The president had little interest in having others manage his time or his words. And Kelly eventually gave up. One leading indicator: All recent White Houses have had daily early-morning senior staff meetings, sometimes a sequence of them. By this year, Kelly’s had dwindled to once a week. Thus Kelly’s departure marks the latest victory for what we might call “competitive adhocracy” in the Trump White House.

To be sure, Trump is not the first president to stir competition among advisers in the hopes of getting better advice: Franklin D. Roosevelt carried off a competitive model with some extended success, but he had a much smaller White House staff and far greater personal mastery of policy detail.

More recently, recall Barack Obama’s touted “team of rivals” staffing model. In the abstract, the idea of generating information by confrontation is appealing. But in practice, Obama found that such a staff structure had high managerial costs, not least his own time, and soon moved to something closer to the standard model. By 2011, in the national security area, he had what some observers suggested was a not a team of rivals but a “corps of consensus.”

Back in 2012, Trump tweeted of the dangers of high-level staff turnover, taunting Obama that his three chiefs of staff in three years were part of why he “can’t manage to pass his agenda.” But that result was far more closely linked to the fact that Obama faced a divided government after 2010 — as Trump will discover in 2019.

CNN reports that  Trump ejected Kelly at least in part for just that reason: With the Democrats coming in and the Mueller investigation heating up, Capitol Hill’s dynamics will change dramatically. A former White House official told Politico that Kelly was “the least political person in Washington holding the most political job in Washington. You need a bona fide Machiavellian killer.”

Maybe so. The lessons of Trump’s first two chiefs of staff suggest that the third one will indeed have to be a Machiavellian master — but  first and foremost, of Oval Office politics.