Donald John Trump Sr. needs all the friends he can find on Capitol Hill.

Why, then, does the president of the United States insist on waging rhetorical war with the leader of the U.S. Senate’s Republican majority? Why is he picking a fight with Mitch McConnell, a master Senate parliamentarian and a guy known as one who can move legislation?

That’s what Trump is doing.

I’m going to put my money on McConnell getting the better of this battle of wits.

McConnell was mildly critical of the president for setting “excessive expectations” for his legislative agenda. Trump then fired back — via Twitter, of course! — this message: “Senator Mitch McConnell said I had ‘excessive expectations,’ but I don’t think so. After 7 years of hearing Repeal & Replace, why not done?”

You see, this is another demonstration of what the president fails to acknowledge. He is the leader of the Republican Party. He’s the head of the executive branch of government. He owns the GOP’s failure to enact an Affordable Care Act replacement bill as much as the congressional Republican leadership.

Except that he refuses to take ownership on that failure. Or any failure, for that matter.

This deteriorating relationship is going to bring great harm to the president’s ability to enact any kind of legislative agenda. The more he fights with members of his own party, the weaker he appears across the land.

Democrats, meanwhile, should follow the time-honored credo of refusing to butt in when principals of the other party are fighting so openly.

What’s more, if the special counsel’s investigation into that “Russia thing” gets any hotter, and it produces actionable results, the president is going to seriously need friends on his side of the aisle. This intra-Republican squabbling isn’t going to help him.

This might be where I should say: Awww, cry me a river.