Rich Lowry: Why John Kelly Is Irreplaceable

If John Kelly didn't exist, President Donald Trump would have to invent him, and he wouldn't be able to.

The chief of staff had a rocky couple of weeks with the imbroglio over ousted White House staff secretary Rob Porter, but he is as close as it gets to an indispensable man in the Trump White House.

Where else is the president going to find someone whom he likes and respects (at least on most days), who can intimidate the White House staff into a semblance of order, who has experience in wielding responsibility in even more difficult circumstances, and who shares Trump's instincts?

The last...