Defense Secretary Jim Mattis might get the boot, if you take seriously what he said on Sunday. That would be bad.

Trump called the retired general a Democrat in a "60 Minutes" interview, and prompted speculation about Mattis's tenure and just how long one of the few original members of the president’s Cabinet would keep his job. Trump, however, would do well to keep Mattis in the job as long as he’ll stay.

During the televised interview, when asked about the possibility of Mattis leaving, Trump responded, “Well, I don’t know.... He hasn’t told me that. I have a very good relationship with him, I had lunch with him two days ago. It could be that he is. I think he’s sort of a Democrat, if you want to know the truth.”

Although he followed those statements up saying that Mattis was a “good guy” and explaining “I mean, at some point, everybody leaves.” Calling him a Democrat definitely wasn’t a compliment and is a sign of a potentially growing rift between the Department of Defense and the White House.

[Related: Jim Mattis 'laser-focused on doing his job' amid Trump talk on his future, politics]

Indeed, Mattis is regarded as one of the few officials who can and will push back against the president – although he tends to do so out of the public eye and has avoided picking public fights with the commander-in-chief, preferring a level –headed professional approach to the job.

Mattis set himself a daunting tasking: ensuring that the U.S. military remain the best force in the world and that it was prepared the meet future challenges. His dedication to this goal has set the country on the right track and, importantly, has added experience and expertise to an administration that had little to begin with.

This is the sort of leadership that the U.S. needs.

Facing new challenges from rising powers including China and Russia, the wars fought today are likely poor indicators of future conflicts. Mattis is also right to support new military technology, like the new Futures Command, rather than Trump’s idea of a flashing Space Force – an idea of which Mattis has remained skeptical.

Moreover, Mattis has made a priority of bolstering the lethality of the U.S. military and has worked to keep key alliances, such as NATO, strong even in the face of criticism from Trump. Additionally, he has tried to reform DoD spending practices and cut waste in spending.

Those efforts not only serve the country well in the present but also set the U.S. up for long term success and increased readiness. That fits right in with Trump’s plan to put America first and bolster the military.

If Trump is serious about maintaining the United States as a force to be reckoned with, he’d be hard-pressed to find a better man to lead that effort than Mattis. There are few others who would be happy to work in his administration, bring his range of experience and be comfortable correcting the president when it matters most.

Trump made a good choice in picking Mattis, and he would be wise to keep him in his Cabinet.