Call it the triumph of hope over experience, at least in the short run. John Kelly took the oath of office and formally replaced Reince Priebus as Donald Trump’s chief of staff, as turmoil at the White House has created distractions from the president’s agenda. The former Marine commander will instill more discipline within the White House — if he’s allowed to do so. The question is less whether Kelly can impose it downwards than whether it will be accepted upwards:

WATCH: President Trump announces swearing in of Gen. John Kelly as new White House chief of staff https://t.co/TyA0EVm8sF

— NBC News (@NBCNews) July 31, 2017

President Trump on Monday swore in retired four-star Marine Corps Gen. John Kelly as his new chief of staff.

Sitting beside Kelly in the Oval Office, Trump predicted the former Homeland Security secretary would do a “spectacular job” leading the West Wing and advancing his stalled agenda.

“We look forward to — if it’s possible — an even better job as chief of staff,” Trump told reporters.

Kelly didn’t waste any time getting his feet wet, attending his first Cabinet meeting as chief of staff immediately afterward. Few doubt the discipline that Kelly will bring to his new job, but the question is whether Trump will embrace that discipline. Yesterday, Kellyanne Conway didn’t provide an answer as to whether she and Anthony Scaramucci will have to report to Kelly rather than directly to Trump, which will be a key indicator of just how serious Trump is in righting the ship at the White House. “This Marine understands the chain of command,” NBC’s analyst concludes, but it’s still a “colossal if” as to whether Trump will respect it:

Chuck Todd writes that Trump’s closest allies don’t give much hope for that colossal if:

Former Trump campaign chief Corey Lewandowski told one of us on Sunday that “anybody who thinks they’re going to change Donald Trump doesn’t know Donald Trump,” advising incoming chief of staff Gen. John Kelly to skip any attempts to modify the president’s style.

The challenge for Kelly, as famous for his discipline as he may be, is that the root of the White House chaos is the nurturing of rivalries and the unpredictability that comes from the president himself.

That’s more about style than structure, but Lewandowski’s observation applies to both to some extent. Trump has run his businesses for decades with a certain amount of chaotic competition between underlings, which works better in a family-run business where all authority exists at the top of the pyramid than it does in shared-power structures like the federal government and its bureaucracies. If Kelly is going to make any impact at all on the chaos, he has to become the gatekeeper to Trump and to force everyone to report through him. Trump never gave “Reincey” the juice to demand and enforce that kind of discipline. If Trump won’t allow that for Priebus’ successor either, then Kelly’s wasting his time.

No one knows that better than Kelly does, though, and it seems very doubtful that he’d give up a Cabinet office to take this thankless job without reaching an agreement on that point. That kind of discipline would also be necessary to start plugging leaks and forcing others to act in a more disciplined manner. That may be what sold Trump on that kind of change. We’ll know whether Kelly takes control by who leaves the White House next, and whether the environment changes from absurdly antagonistic to mission-focused professionalism.