James “Mad Dog” Mattis has been considered one of the grownups of the Trump administration.

The defense secretary now reportedly is preparing to recommend that transgendered Americans be allowed to serve in the U.S. military.

Is the president listening? Is he prepared to heed the advice of this retired Marine Corps general he named to lead the Pentagon?

Let us hope so.

Trump tweeted a policy change in 2017 in which he declared his intention to ban transgendered troops from serving or transgendered Americans from seeking to serve in the military.

Imagine that. The commander in chief would deny patriotic Americans who want to defend their country the chance to fulfill their duty as citizens of the greatest nation on Earth. The president offered some lame rationale about the huge medical costs associated with transgendered troops.

What critics pointed out was that the Pentagon spends many times more for drugs to cure troops of erectile dysfunction than it spends on transgendered troops.

Now it’s up to the defense secretary, a man with considerable combat experience, to remind the president that transgendered Americans are serving with pride and professionalism alongside other patriots.

Let’s hope the president hears him.

Isn’t it just amazing that a Cabinet secretary with the nickname “Mad Dog” could be so, um, rational?