Donald Trump has shown just how incapable he is of telling the truth.

The president of the United States has enormous power within the executive branch of government. He knows it. I know it. You know it. He can do virtually anything he wants, providing he isn’t breaking the law.

Granting security clearances, even to those who don’t deserve them, is fully within the president’s power as the nation’s chief executive.

Why, though, does the president of the United States — Donald John Trump — have to lie about whether he interceded to get his son-in-law, Jared Kushner, a top-secret security clearance?

He said he didn’t do it. He insisted he didn’t force anyone to grant Kushner such a clearance.

But . . . but, he has the power! He would be acting totally within his authority to do so. And he did do what he is empowered to do. By lying about whether he intervened on Kushner’s behalf, the president has doubled his trouble.

Sure, he could be criticized for greasing the clearance for Kushner. Why? Because his son-in-law has no security credentials. He doesn’t deserve access to the kind of information he gets with such a clearance.

Now, though, the president is getting pummeled because he is demonstrating his penchant for gratuitous lying.